By Alice Henshaw, RN, NMP, Founder of SKIN|CYCLES and Harley Street Injectables

This article is written for educational purposes by a qualified nurse prescriber and cosmeceutical formulator. It is not a substitute for personalised medical advice. Skin ageing is influenced by genetics, hormonal status, lifestyle and medical history. If you have specific skin conditions or concerns, please consult your GP or a dermatologist. The products referenced throughout this article are formulations I developed as the founder of SKIN|CYCLES. I am not a neutral reviewer, but I will explain exactly why I made the formulation decisions I did, so you can evaluate the reasoning rather than taking my word for it.

I want to start with something that might sound counterintuitive, given that I am about to walk you through a decade-by-decade guide to skin ageing.

The decades are not the point.

Your skin does not read a calendar. It does not wake up on your thirtieth birthday and decide, right, time to start losing collagen. What actually changes your skin over time is messier than that: a tangle of biology (your genetics, your hormonal status, the particular rate at which your body degrades collagen), environment (UV exposure, pollution, whether you live in London or Dubai), and the cumulative effect of every decision you have made about what goes on your face. Ten years of decisions. Twenty. Thirty. They add up in ways that are not always obvious until, one morning, they are.

So why write a decade guide at all? Honestly, I went back and forth on this. But the biological shifts do cluster in recognisable patterns, even if they do not respect neat birthday boundaries. Collagen^{1CollagenThe main structural protein in the dermis, providing skin its firmness.} production starts its slow, quiet decline somewhere in the mid-twenties. Hormonal changes, particularly the oestrogen^{2OestrogenKey female hormone that stimulates collagen synthesis and skin hydration.} drop that begins in perimenopause, tend to show up in the forties. The post-menopausal collagen cliff? That hits most women somewhere in the early fifties. Patterns, not rules. But understanding the patterns gives you the chance to adjust your approach before the consequences become visible, rather than scrambling to react once they already have.

That is what I want this article to be. Not another list of "best ingredients for your 30s." Those exist everywhere, and honestly, most of them could be swapped for each other without anyone noticing. What I want to offer is the reasoning behind the routine: what is actually happening in your skin at each stage, why, and how a thoughtful approach (right actives, right delivery, right concentrations) can genuinely help. Where the evidence supports it, I will explain how specific SKIN|CYCLES formulations address those mechanisms. Where the evidence is thin, or where I think a professional treatment is the better answer, I will tell you that too.

One more thing before we begin. I formulated every product in the SKIN|CYCLES range. Every single one. That means I have a commercial interest in the recommendations I make, and you should know that upfront. But it also means I can tell you, ingredient by ingredient, why each formulation exists and what problem it was designed to solve. I would rather you understood the reasoning and made your own judgment than took any of this on faith.

What All the Decade Guides Get Wrong

I have read dozens of "skincare by decade" articles. Genuinely, dozens. Most of them follow the same template: SPF in your 20s, retinol in your 30s, richer moisturiser in your 40s, see a dermatologist in your 50s. That advice is not wrong, exactly. It is just so generic that it helps almost nobody.

Here is what bothers me most about them.

They treat ageing as one thing. As if "time" were the variable. But time is not doing the damage. Specific biological processes are doing the damage: collagen degradation, elastin fragmentation, barrier dysfunction, melanocyte^{3MelanocyteCell in the epidermis that produces melanin, responsible for pigmentation.} dysregulation, hormonal withdrawal. Each of these runs on its own timeline, follows its own mechanism, responds to its own intervention. Lumping them all under "anti-ageing" is a bit like treating every illness with the same tablet.

And then there is the delivery problem, which almost nobody talks about. It drives me slightly mad, actually. Telling someone to "use retinol" without explaining that the delivery system determines whether that retinol reaches the dermis or just sits on the surface causing irritation to the stratum corneum^{4Stratum corneumThe outermost layer of the epidermis, the skin's primary barrier.} is incomplete advice. I care about this more than most people, admittedly, because solving this problem with liposomal encapsulation^{5Liposomal encapsulationWrapping actives in lipid spheres for deeper, gentler delivery.} is one of the reasons SKIN|CYCLES exists.

The other glaring gap? Nobody distinguishes between photoageing^{6PhotoageingPremature skin ageing caused by cumulative UV exposure.} and chronological ageing^{7Chronological ageingIntrinsic skin ageing driven by genetics and time, independent of UV.}. These are different processes. Different visible outcomes. Different treatments required. A woman in her forties who spent her twenties sunbathing in Marbella and a woman in her forties who grew up in overcast Manchester with SPF as a daily habit have fundamentally different skin, even though every decade guide gives them identical advice.

I want to do better than that. So let me start with the biology.

Your Thirties: The Decade of Quiet Arithmetic

Here is the awkward truth about your thirties. The damage that will show up in your forties? It is being laid down right now. Quietly. Invisibly. You will not see it for years.

From somewhere around your mid-twenties, your body starts producing roughly 1% less collagen each year. That number gets thrown around a lot in skincare marketing, but the research behind it is genuinely robust. Varani and colleagues at the University of Michigan published a landmark study in 2006 in The American Journal of Pathology showing that fibroblasts^{8FibroblastsDermal cells responsible for producing collagen and elastin.} isolated from young adults (aged 18 to 29) produced significantly more type I procollagen than those from older individuals. The decline was driven by two things happening at once: the cells themselves ageing, and the mechanical environment around them deteriorating as collagen fibres fragment (PMID: 16723701). A double hit.

Now, 1% per year does not sound like much. It really does not. But compound it. Run the numbers. By 35, you have lost somewhere around 10% of your total skin collagen relative to your mid-twenties baseline. Your skin still looks good at this point. Still feels firm, still has that elastic snap. But underneath, the scaffolding is thinning. Think of it like a building with slightly fewer load-bearing beams each year. Structurally fine for now. Less so over time.

Alongside collagen decline, two other changes are underway. Cell turnover^{9Cell turnoverThe rate at which skin sheds old cells and replaces them with new ones.} is beginning to slow. Research published in the Journal of Gerontology by Grove and Kligman found that stratum corneum transit time was approximately 20 days in young adults but lengthened by more than 10 days in older adults (PMID: 6827031). The practical consequence: your skin renews itself less efficiently, dead cells accumulate on the surface for longer, and that fresh, luminous quality of younger skin begins to fade. It is subtle in your thirties. It becomes obvious in your forties.

The other change is cumulative UV damage. Even if you have been reasonably careful about sun protection, the photoageing clock has been running since childhood. The difference between sun-exposed and sun-protected skin in the same individual at age 35 can be striking, and this gap only widens.

So what should your thirties routine actually focus on?

Retinoids, properly delivered. This is the decade to establish a retinoid in your routine if you have not already. Retinol remains the most extensively studied topical active for supporting collagen synthesis and accelerating cell turnover. But (and this is the part most guides skip) the form, concentration and delivery system matter enormously. A retinol serum with no encapsulation technology may irritate the skin surface without ever reaching the dermal fibroblasts where collagen is actually produced. I wrote about this in detail in our article on retinol versus peptides, but the short version is that I formulated the Retinol Youth Serum with liposomal delivery specifically to get the active where it needs to go, with less surface irritation.

Daily broad-spectrum SPF, without exception. I have said this so many times it probably qualifies as a personal catchphrase. No amount of retinol, peptides or antioxidants will outrun unprotected UV exposure. The DNA Defence Sun Shield was formulated to provide high-factor protection with antioxidant support. Our article on daily DNA defence explains the reasoning. But the brand does not matter as much as the habit. Wear SPF 30 or higher every day. Reapply. This is the single highest-return investment in your skin's future.

Antioxidant layering. Free radical damage from UV, pollution and blue light accumulates throughout your thirties. An antioxidant serum in the morning, beneath your SPF, provides a second line of defence. We covered the rationale for this in our piece on antioxidant plus SPF shielding for city skin. The glutathione component of our TGHA4® complex is part of this antioxidant strategy, but frankly, any well-formulated vitamin C or antioxidant serum will contribute meaningfully at this stage.

Hydration that goes beyond the surface. Your skin is still producing reasonable amounts of natural hyaluronic acid and sebum^{10SebumNatural oil produced by sebaceous glands, decreasing with age.} in your thirties, so the heavy occlusives can wait. What you want is a lightweight hydrator that maintains barrier integrity without congestion. Bio-Balance was designed for exactly this purpose.

Your Forties: The Hormonal Inflection Point

If your thirties were about quiet arithmetic, your forties are about compound interest coming due, with an additional variable that changes everything: hormones.

Perimenopause typically begins in the early-to-mid forties, though it can start in the late thirties for some women. (I want to be clear about this: the timelines I am giving are averages. Hormonal transitions affect every woman differently, and if you are experiencing symptoms, please speak to your GP or a menopause specialist rather than relying on any skincare article, including this one.)

The reason perimenopause matters for skin is oestrogen. Oestrogen is not a minor player in skin health. It stimulates the production of procollagen (the precursor to collagen), increases elastin^{11ElastinProtein providing skin its ability to stretch and snap back.} and fibrillin levels, and suppresses the enzymes (matrix metalloproteinases) that break collagen down. When oestrogen levels begin to fluctuate and decline, this entire system is disrupted.

A review published in Gynecological Endocrinology by Calleja-Agius and Brincat (2012) described a strong correlation between skin collagen loss and oestrogen deficiency, noting that oestrogen replacement after menopause increased collagen content, dermal thickness and elasticity (PMID: 21970508). A related paper by the same group in Best Practice & Research Clinical Obstetrics & Gynaecology (2013) reinforced that this collagen loss correlated more closely with duration of oestrogen deficiency than with chronological age alone (PMID: 23850161).

What does this mean in practical terms? The collagen decline that was running at roughly 1% per year in your thirties begins to accelerate. Your skin barrier^{12Skin barrierThe stratum corneum and its lipid matrix, protecting against water loss.} function starts to weaken as ceramide^{13CeramidesLipids in the stratum corneum essential for barrier integrity and hydration.} production slows and transepidermal water loss^{14TEWLTransepidermal water loss: moisture escaping through a weakened barrier.} (TEWL) increases. Skin that felt comfortable on a simple routine may suddenly feel dry, reactive, or both. Pigmentation can become more erratic. Texture changes. The skin you thought you knew starts behaving unpredictably.

I went through this myself. There was a morning, I must have been 42 or 43, when I looked at my face in the bathroom mirror and genuinely thought: who moved the goalposts? Same products. Same routine. Same lifestyle, more or less. But the skin looking back at me was behaving like a stranger. Drier in places that had never been dry. Reactive to things it had always tolerated. A kind of dullness that no amount of exfoliation seemed to shift. And remember, I formulate skincare for a living. If I was caught off guard, most women have no chance of anticipating this.

That period crystallised something I had been circling as a formulator. The products I was building needed to do more than address "ageing" as a vague, catch-all concept. They needed to target the specific hormonal mechanisms that drive the steepest phase of decline. The part that nobody warns you about.

The TGHA4® complex, which is the foundation of the SKIN|CYCLES range, was built with this in mind. The four peptides (Argireline, Acetyl Tetrapeptide-5, Palmitoyl Hexapeptide-12, Glutathione) each address a different mechanism that becomes more relevant as oestrogen declines. Argireline modulates neuromuscular signalling to soften expression lines that deepen in the forties. Palmitoyl Hexapeptide-12 supports collagen synthesis. Glutathione provides antioxidant defence against the oxidative stress that increases as the skin's own defences weaken. You can read the full science behind this in our Inside TGHA4® article.

But let me be honest about something. No topical product will replace the collagen your body has stopped making. What it can do is slow the rate of further loss, support the fibroblasts that are still active, strengthen a barrier that is under hormonal siege, and protect against the oxidative damage that accelerates the whole process. That is a meaningful contribution, but it is not a cure. Anyone who tells you otherwise is selling you a story.

So what should your forties routine look like? Different from your thirties. Noticeably different.

The biggest shift is adding peptides alongside your retinol, not instead of it. I get asked this constantly: "Should I switch from retinol to peptides?" No. Use both. Retinol drives turnover and tells your fibroblasts to keep producing collagen. Peptides give those same fibroblasts the amino acid building blocks they need to actually make it. Two different jobs. Both essential. I went into this in depth in our article on retinol versus peptides. The Collagen Renewal Complex was specifically designed to pair with retinol, not replace it.

Your barrier needs more attention now too. This is the thing that catches people off guard. A compromised barrier cannot retain the actives you are applying, cannot hold hydration, and worst of all, it creates a cycle of sensitivity that makes you give up on the very ingredients your skin most needs. I have seen it happen so many times: a woman in her forties starts retinol, her barrier reacts, she stops everything, and her skin gets worse. Bio-Balance and 5D HA together provide the multi-weight hydration and barrier support that prevents this cycle. The Age Defence Complex adds targeted peptide activity on top.

Pigmentation becomes a different beast in your forties. Melanocytes start behaving less predictably. That sun damage you accumulated in your twenties and thirties, the damage you could not see? It surfaces now. Uneven tone, dark spots, a mottled quality that foundation cannot quite hide. SPF remains the single most important defence, but adding targeted antioxidants and careful, gentle exfoliation can help manage what has already emerged.

One more thing. Your eye area deserves its own strategy at this stage. The periorbital skin is the thinnest on the face, loses elasticity first, and shows hormonal changes before anywhere else. I wrote about this in our Bright Eyes and Fuller Lips article.

Your Fifties: The Collagen Cliff and What Comes After

If there is a single statistic I want every woman over 45 to know, it is this one.

Women can lose up to 30% of their skin collagen in the first five years after menopause.

This figure appears consistently across the dermatological literature. Brincat and colleagues, in a seminal 1987 study published in Obstetrics & Gynecology, measured skin collagen content, skin thickness and bone mass in postmenopausal women and found a decline of between 1-2% per year after menopause, with significant correlations between all four parameters (PMID: 3120067). A review by Thornton (2013) in Dermato-Endocrinology cited that type I and III skin collagen is thought to decrease by as much as 30% in the first five years after menopause, paralleling the reduction in bone mass observed in the same period (PMC3772914). And a comprehensive review published in Climacteric (2022) confirmed that skin collagen levels decrease fairly rapidly in early menopause, with approximately 30% reduction in the first five years, followed by a further decline of around 2% per year for the subsequent 15 years (Kamp et al., 2022).

Let me put that number in context, because it is the kind of statistic that slides past you if you are not paying attention.

Say you entered menopause with about 75% of the collagen you had at 25. That is a reasonable estimate after decades of the slow, 1%-per-year background erosion. Now lose 30% of that remaining 75% in five years. You are down to roughly half of what you started with. Half. In half a decade. That is not a gentle, graceful fading. That is a cliff edge.

And it explains something I hear constantly from women in their late forties and early fifties: "My skin changed overnight." It did not, of course. The hormonal trigger simply lit the fuse on a process that had been building for twenty-five years. But the subjective experience, the looking-in-the-mirror-and-not-recognising-yourself experience, is very real. The skin suddenly feels thinner. Drier. Less forgiving. More fragile. I have had this conversation hundreds of times in clinic, and it never gets less important.

Beyond collagen, the fifties bring several other shifts. Sebum production drops significantly, which means naturally drier skin that can no longer rely on its own lipids for barrier protection. Ceramide levels in the stratum corneum decline, further compromising barrier function. Cell turnover, already slowing since your thirties, drops more dramatically after 50. Grove and Kligman's research suggested the decline in epidermal renewal may remain relatively constant in younger years and then drop sharply after age 50 (PMID: 6827031). The practical result: skin looks duller, heals more slowly, and is more vulnerable to environmental insult.

Glycation^{15GlycationSugar molecules bonding to proteins, stiffening collagen fibres.} also accumulates. This is the process by which sugar molecules bond to collagen and elastin fibres, creating cross-links that make these proteins stiff and brittle. Glycated collagen cannot flex or remodel normally. Advanced glycation end products (AGEs^{16AGEsAdvanced glycation end products: sugar-damaged proteins that accelerate ageing.}) accumulate with age and contribute to the characteristic loss of skin suppleness in the fifties and beyond.

This is the decade where I have the most honest and sometimes difficult conversations with my clients. Because the truth is that topical skincare alone cannot fully address the magnitude of change that is happening. It can contribute meaningfully. It can support what remains. It can protect against further damage. It can make a genuine visible difference to hydration, radiance, texture and comfort. But if a woman comes to me at 55 expecting a serum to undo five years of post-menopausal collagen loss, I would rather be honest than make a sale.

What topicals CAN do in your fifties, and do well:

Hydration, first and foremost. Not the single-ingredient kind. Your fifties skin needs hydration that works at multiple depths simultaneously, which is exactly why I formulated the 5D HA serum with five molecular weights of hyaluronic acid. This is not a marketing gimmick. Larger HA molecules form a moisture-retaining film on the surface. Smaller ones penetrate into the epidermis. In your thirties, a single-weight HA serum was probably fine. Now? You need the full spectrum. Your skin is losing water faster than it can replace it, and a lightweight hydrator alone will not cut it anymore.

Sleep becomes your secret weapon. I mean this literally. Your skin's repair mechanisms peak overnight: cell division rates climb, growth hormone levels rise, and the dermis enters what amounts to a nightly maintenance cycle. The ExoYouth Sleep Mask was built for this window. It creates an occlusive, nutrient-dense environment that works with your skin's own circadian rhythm rather than against it. I discussed the science behind nocturnal skin biology in our article on the 4-6 week skin cycle.

Your cleanser, meanwhile, matters far more than you probably think. This is counterintuitive. People obsess over serums and forget that a stripping cleanser can undo half the work overnight. At this stage, your barrier cannot bounce back from a harsh surfactant the way it did twenty years ago. The Squalane Cream Cleanser does the job without dismantling the lipid matrix your skin can no longer easily rebuild.

Retinol? Keep using it. Do not stop. I see women abandon retinol in their fifties because their skin feels "too sensitive." Usually, the issue is not the retinol itself. It is the supporting routine around it. Drop to two or three nights a week, layer serious hydration over the top, and make sure your delivery system is gentle enough for thinner, more reactive skin. The benefits of retinol (turnover, collagen signalling) are more important in your fifties than they have ever been.

And then there is the conversation I have more often than any other at the clinic. If your primary concern is significant volume loss, deep structural wrinkles, or laxity that no cream will tighten, the most honest thing I can tell you is: go see someone. The best skincare routine in existence will not replicate what a skilled aesthetic practitioner can achieve with targeted treatments. At Harley Street Injectables, I see women in their fifties every single week, and the plans that produce the best results almost always combine excellent daily skincare with professional intervention. The skincare protects and maintains. The treatments reach what topicals physically cannot.

The TGHA4® Advantage Across Decades

I want to explain something about the way I think about formulation, because it matters for understanding why the SKIN|CYCLES range is built the way it is. Bear with me. This is the part where I get genuinely excited about chemistry, which I realise is not everyone's idea of a good time.

Most skincare brands create one line for "young" skin and another for "mature" skin, as if there were some clean dividing line at 40 where you graduate from one shelf to the next. I have always found that approach frustrating. In clinic, what I see is a continuum. The mechanisms of ageing do not politely wait their turn. They run in parallel, all of them, from your mid-twenties onward. Collagen loss, oxidative stress, barrier weakening, expression-line deepening. All happening simultaneously, just at different speeds. What shifts decade by decade is not which mechanisms are active but which ones are loudest.

That observation is what led to TGHA4®. Four peptides, each addressing a different mechanism. Argireline targets neuromuscular signalling (the expression lines that start deepening in your thirties and really settle in by your forties). Palmitoyl Hexapeptide-12 supports collagen synthesis directly. Acetyl Tetrapeptide-5 works on periorbital fluid retention, a problem that gets worse as barrier function declines. Glutathione provides broad antioxidant cover against the oxidative stress that increases year on year as your skin's own defences thin out.

In your thirties, the glutathione and Argireline are probably doing most of the noticeable work. By your forties, the collagen-support peptides have moved to the foreground. By your fifties, frankly, you need all four firing at once. The Inside TGHA4® article goes deep on the peptide science. The point I want to make here is simpler: build a complex that addresses several mechanisms at once, and the same technology stays relevant as your biology changes. That was the design brief. I think it works. But I would rather you read the evidence and decide for yourself.

On evidence: a 2025 review of acetyl hexapeptide-8 (Argireline's active) published in the International Journal of Molecular Sciences confirmed it can modulate neuromuscular activity topically. One of the reviewed studies reported wrinkle depth reductions of up to 30% after four weeks (PMC12193160). Separately, a 2023 clinical study using Visia imaging analysis found measurable improvements in skin surface texture from an Argireline-containing serum (PMC10665711). These are not miracle numbers. I perform injectable treatments at my clinic every day, and topical peptides do not produce the same magnitude of change. But they produce real, measurable, consistent change without needles, downtime, or clinic visits. For a lot of women, that trade-off makes sense.

Building Your Decade-Specific Routine

Right. Theory is done. Let me make this practical. Here is how I would actually structure a routine for each decade. I am using the 4-6 week skin cycle as the underlying framework, because it gives you a realistic timeline for seeing results rather than the "instant glow" nonsense that clutters most skincare advice.

Your Thirties: Prevention and Protection

Keep it simple. Mornings: a gentle cleanser, an antioxidant serum, Bio-Balance for hydration, and DNA Defence Sun Shield. Every single day. I cannot stress this enough. No "oh, it is cloudy, I will skip it." No.

Evenings are even simpler: cleanse, apply Retinol Youth Serum (twice weekly at first, gradually building to alternate nights), then Bio-Balance over the top. Once a week, add a gentle exfoliation and a hydrating mask when your skin tells you it needs one.

The governing principle here? Consistency beats intensity. Four products used faithfully for three years will do more for your skin than twelve products used sporadically for three months.

Your Forties: Support and Strengthen

Now the routine gets more layered, because it needs to. Mornings: swap to Squalane Cream Cleanser (your barrier may no longer tolerate that foaming cleanser you have used since university). Follow with 5D HA, then either Age Defence Complex or Collagen Renewal Complex, and always finish with DNA Defence Sun Shield.

Evenings: cleanse, Retinol Youth Serum on alternate nights (peptide treatment on the off-nights), Bio-Balance, and ExoYouth Radiance Cream for that extra layer of overnight support. Weekly, a Bio-Cellulose Mask for intensive hydration. (Our article on bio-cellulose versus cotton sheet masks explains why the mask material itself matters more than most people realise.)

The shift from your thirties routine to your forties routine is not about using more for the sake of it. Each additional layer addresses a mechanism that was not yet dominant ten years ago but is now.

Your Fifties: Repair and Protect

This is the most involved routine, and it should be. Mornings: Squalane Cream Cleanser, 5D HA, Collagen Renewal Complex, ExoYouth Radiance Cream, DNA Defence Sun Shield. Yes, five steps. Your skin needs them.

Evenings: double cleanse with ExoYouth Cleansing Balm followed by Squalane Cream Cleanser. Retinol Youth Serum two or three nights a week (always with hydration layered generously over the top). 5D HA. Seal everything in with the ExoYouth Sleep Mask. Weekly, a Bio-Cellulose Mask, and very gentle exfoliation, less often than in your forties, because the barrier simply cannot take it.

The principle in your fifties is depth, not frequency. Richer formulations. Fewer active rotations. And treating sleep not as downtime but as an active treatment window, because biologically, that is exactly what it is.

My earlier piece on my go-to serum routine walks through the layering logic in more detail, if you want the granular version.

What I Wish I Had Known Earlier

I am going to end with something personal, because honestly, I think it will be more useful than one more paragraph of dermatology.

I wish someone had grabbed me by the shoulders in my early twenties and said: that SPF you keep "forgetting"? It is going to come back as pigmentation in your forties, and you are going to spend real money and real time trying to undo it. I wish someone had explained that the "glow" everyone talks about in younger skin is not some mystical quality. It is a measurable function of collagen density and cell turnover rate, and both of those have a biological clock ticking away whether you acknowledge it or not. And I really wish I had understood, much earlier than I did, that the skin barrier is not just some passive wrapper. It is a living, active system. Maintaining it is the single most impactful thing you can do for the efficacy of everything else you layer on top.

I know these things now because I have spent the better part of two decades treating skin professionally and, in parallel, formulating products to address the problems I see on a daily basis. But I also know them because I have lived them. Watched them play out on my own face, year by year. That dual perspective (practitioner and participant, formulator and consumer) is what I have tried to bring to this article.

If you take one thing away from all of this, let it be this: there is no right age to start. If you are 30, you have time. Use it well. If you are 50 and thinking "I should have started this years ago," start now. Today. Your skin is not a fixed entity. It responds to what you give it. Slowly, yes. More slowly than it did at 25. But the response is real. Measurable. Worth the effort.

And if you have reached a point where topical skincare alone is not enough? That is not a failure on your part. That is just biology being biology. The best results I see, across every age group, come from people who pair excellent daily skincare with honest, skilled professional guidance. That is exactly why I built both SKIN|CYCLES and Harley Street Injectables. They were always meant to work together. Two halves of the same thinking.

Retinol and retinoid products can cause photosensitivity and are not recommended during pregnancy or breastfeeding. Always patch-test new actives and introduce retinoids gradually (twice weekly, building over several weeks). No sunscreen provides 100% UV protection; reapply every two hours during sun exposure. Individual results from any skincare product will vary based on skin type, genetics, lifestyle and consistency of use.

Alice Henshaw

RN · NMP · Founder of SKIN|CYCLES & Harley Street Injectables

Alice is the founder of SKIN|CYCLES, a cosmeceutical skincare range formulated around the proprietary TGHA4® peptide complex and sold at Harrods, Liberty and Harvey Nichols. She is also the founder and medical director of Harley Street Injectables, the largest clinic on Harley Street dedicated exclusively to non-surgical aesthetic treatments. A qualified nurse prescriber registered in the UK, Australia and New Zealand, Alice is a Key Opinion Leader for Allergan Aesthetics, was named Best Aesthetic Injector in London by the GHP Awards, and has been featured in Vogue, Tatler, Vanity Fair, and the Tatler Cosmetic Surgery Guide.

LinkedIn Instagram @skincycles

To explore the SKIN|CYCLES range, visit skincycles.com. To book a consultation at Harley Street Injectables, visit harleystreetinjectables.com or call +44(0) 3455 485 658.

Sources referenced in this article:

1. Varani, J., Dame, M.K., Rittie, L., Fligiel, S.E.G., Kang, S., Fisher, G.J., Voorhees, J.J. (2006). "Decreased collagen production in chronologically aged skin: roles of age-dependent alteration in fibroblast function and defective mechanical stimulation." The American Journal of Pathology, 168(6), 1861-1868. PMID: 16723701. DOI: 10.2353/ajpath.2006.051302. University of Michigan study demonstrating age-dependent fibroblast decline.

2. Grove, G.L., Kligman, A.M. (1983). "Age-associated changes in human epidermal cell renewal." Journal of Gerontology, 38(2), 137-142. PMID: 6827031. DOI: 10.1093/geronj/38.2.137. Foundational study on stratum corneum transit time and epidermal proliferation decline with age.

3. Calleja-Agius, J., Brincat, M. (2012). "The effect of menopause on the skin and other connective tissues." Gynecological Endocrinology, 28(4), 273-277. PMID: 21970508. DOI: 10.3109/09513590.2011.613970. Review of oestrogen deficiency and connective tissue changes at menopause.

4. Calleja-Agius, J., Brincat, M. (2013). "Skin connective tissue and ageing." Best Practice & Research Clinical Obstetrics & Gynaecology, 27(5), 727-740. PMID: 23850161. DOI: 10.1016/j.bpobgyn.2013.06.004. Comprehensive review of skin collagen decline and oestrogen correlation.

5. Brincat, M., Kabalan, S., Studd, J.W., Moniz, C.F., de Trafford, J., Montgomery, J. (1987). "A study of the decrease of skin collagen content, skin thickness, and bone mass in the postmenopausal woman." Obstetrics & Gynecology, 70(6), 840-845. PMID: 3120067. Seminal study establishing 1-2% annual post-menopausal collagen decline.

6. Thornton, M.J. (2013). "Estrogens and aging skin." Dermato-Endocrinology, 5(2), 264-270. PMID: 24194966. PMC: PMC3772914. DOI: 10.4161/derm.23872. University of Bradford review citing up to 30% type I and III collagen loss in first five post-menopausal years.

7. Kamp, E., Ashraf, M., Musbahi, E., DeGiovanni, C. (2022). "Skin, hair and beyond: the impact of menopause." Climacteric (via Taylor & Francis). Full text. Review confirming 30% collagen reduction in first five years, then 2% per year for 15 years.

8. Blanes-Mira, C., Clemente, J., Jodas, G., Gil, A., Fernandez-Ballester, G., Perez-Paya, E., Ferrer-Montiel, A. (2002). "A synthetic hexapeptide (Argireline) with antiwrinkle activity." International Journal of Cosmetic Science, 24(5), 303-310. And review in International Journal of Molecular Sciences (2025). PMC: PMC12193160. Review of acetyl hexapeptide-8 efficacy and skin permeation.

9. Sheridan, A.T., et al. (2023). "Investigating the effects of Argireline in a skin serum containing hyaluronic acids on skin surface wrinkles." Experimental Dermatology. PMC: PMC10665711. Clinical study using Visia analysis for Argireline-containing formulations.

10. Sibilla, S., et al. (2015). "Skin collagen through the lifestages: importance for skin health and beauty." Plastic and Aesthetic Research, 2, 153. Full text. Review of collagen content peaking at 25-34 and declining approximately 25% over four decades.

Further reading from SKIN|CYCLES:

• The 4-6 Week Skin Cycle, the foundational article on how skin renewal works and why patience matters.
• Retinol vs Peptides, an honest comparison of the two most important anti-ageing actives.
• Inside TGHA4®, the full science behind the four-peptide complex at the heart of every SKIN|CYCLES formulation.
• My Go-To Serum Routine, a practical guide to layering serums for maximum efficacy.