Science & technology | Well Informed The chemicals that reduce wrinkles Vitamins, applied properly, can partially reverse the effects of ageing Jun 5th 2026|3 min read  ABIOCHEMISTRY textbook sometimes feels like essential reading when shopping for wrinkle-reducing products. Their labels list molecules like retinoids, antioxidants, peptides and exfoliating acids. The names might be familiar, but does anyone know what they do? Many of the claims that they will make skin appear more youthful rely on company-funded studies or consumer surveys rather than rigorous clinical evidence. Yet a handful of ingredients do have a solid scientific backing. Older-looking skin comes about via two distinct processes: the passage of time and environmental damage caused by ultraviolet (UV) light, pollution and smoking. All of these harm the collagen and elastin fibres in the extracellular matrix, the skin’s structural scaffolding, causing wrinkles and sagging. Around 80% of ageing in white skin is caused by UV exposure, according to Abigail Langton, a dermatology researcher at the University of Manchester—the melanin in darker skin provides some degree of protection. If your wrinkles worry you, then the ingredient with the strongest scientific backing that might help is tretinoin, also known as all-trans retinoic acid. A derivative of vitamin A, it was originally developed as a treatment for acne, but in the mid-1980s dermatologists noticed that patients who used it had fewer wrinkles as well as fewer spots. Studies of skin biopsies, as well as non-invasive skin imaging, revealed that tretinoin thickens the epidermis, the skin’s outer layer, making it look smoother and improving fine lines. It also stimulates collagen production in the dermis, the layer that sits just under the epidermis. This seems to partly restore the extracellular matrix and reduce wrinkles. Tretinoin is generally only available on prescription and it can irritate the skin. Milder retinoids—molecules derived from vitamin A—such as retinol and retinal, are used in over-the-counter creams and serums. Once they are absorbed by the skin, these chemicals are converted into tretinoin. Pricier formulations often contain those derivatives that convert more easily or are more stable. Although over-the-counter retinoids are less aggressive, it is still sensible to start with a lower concentration (those as low as 0.04% can be effective) and work up to avoid irritation. There is also support for the anti-ageing effects of certain antioxidants, chiefly vitamin C (ascorbic acid). This plays an important role in collagen production, and there is evidence it can reduce wrinkles and hyperpigmentation. The downside is that it is unstable and can break down quickly if products are not formulated or stored correctly. An expensive cream can become ineffective if it is left lying around for too long. Peptides, another common ingredient, are short chains of amino acids. Some encourage the production of extracellular matrix proteins, others prevent their breakdown and some relax the face muscles, in a manner similar to botox. The scientific studies used by cosmetics companies to claim anti-wrinkle benefits are, however, typically conducted or funded by those same companies. All these ingredients can be, and are, combined in different ways. And they need time to work: dermatologists recommend sticking with the same regimen for several months before judging the results and making any tweaks. But though these ingredients may partly reverse the signs of ageing, prevention is more effective. Nothing beats protecting yourself against the sun.■   科學與技術｜知識充電站 減少皺紋的化學成分 正確使用維他命，可以部分逆轉老化帶來的影響。 在購買抗皺產品時，有時候會讓人覺得好像必須先讀懂一本生物化學教科書才行。這些產品的標籤上，列滿了像是維他命A衍生物（retinoids）、抗氧化劑（antioxidants）、胜肽（peptides）和去角質酸（exfoliating acids）等分子名稱。這些名字聽起來可能很神祕，但真的有人知道它們的功效是什麼嗎？許多宣稱能讓肌膚看起來更年輕的說法，往往只依賴公司資助的研究或消費者問卷調查，而不是嚴謹的臨床證據。不過，確實有少數幾種成分擁有紮實的科學理論支持。 皮膚顯得老化主要是由兩個不同的過程造成的：時間的流逝，以及由紫外線（UV）、污染和抽菸所引起的環境傷害。這所有因素都會破壞細胞外基質（也就是皮膚的結構支架）中的膠原蛋白與彈性纖維，進而導致皺紋和下垂。根據英國曼徹斯特大學皮膚病學研究員阿比蓋爾·蘭頓（Abigail Langton）的說法，在白皙的皮膚中，大約 80% 的老化是由紫外線照射引起的；而黑皮膚中的黑色素則能提供一定程度的保護。 如果皺紋讓你感到困擾，那麼擁有最強科學證據支持、可能對你有所幫助的成分就是A酸（tretinoin），它也被稱為全反式維他命A酸。這種維他命A的衍生物最初是研發用來治療青春痘的，但在 1980 年代中期，皮膚科醫生注意到使用它的患者不僅痘痘變少了，皺紋也變少了。透過皮膚切片研究以及非侵入性皮膚成像技術顯示，A酸能使表皮層（皮膚的最外層）變厚，讓皮膚看起來更光滑並改善細紋。它還能刺激真皮層（緊鄰表皮層下方的組織）產生膠原蛋白。這似乎能部分修復細胞外基質並減少皺紋。 A酸通常屬於處方藥，且可能會刺激皮膚。因此，較溫和的維他命A衍生物（例如A醇 retinol 和A醛 retinal）常被用於市售的免處方乳霜和精華液中。當這些化學成分被皮膚吸收後，會轉化為A酸。價格較昂貴的配方通常含有更容易轉化或更穩定的衍生物。雖然市售的A醇或A醛產品比較沒有那麼強烈，但一開始最好還是先從較低的濃度（低至 0.04% 就能發揮效果）開始使用，然後循序漸進，以避免皮膚發炎刺激。 某些抗氧化劑的抗老化效果也得到了支持，其中最主要的成分是維他命C（抗壞血酸）。它在膠原蛋白的生成中扮演著重要的角色，且有證據顯示它能減少皺紋和黑色素沉澱（hyperpigmentation）。缺點是它非常不穩定，如果產品的配方不對或存放方式不當，它很快就會分解失效。如果把昂貴的乳霜隨便亂放太久，它可能會變得完全沒有效果。 胜肽是另一種常見的成分，它是胺基酸的短鏈。有些胜肽能促進細胞外基質蛋白的生成，有些能防止它們分解，還有一些則能放鬆面部肌肉，其作用方式類似於肉毒桿菌。然而，化妝品公司用來宣稱抗皺功效的科學研究，通常都是由這些公司自己進行或資助的。 所有這些成分都可以、也確實被以不同的方式組合在一起。而且它們需要時間才能發揮作用：皮膚科醫生建議，在評估效果並進行任何調整之前，應該堅持使用相同的護膚流程幾個月。雖然這些成分可以部分逆轉老化的跡象，但預防依然比治療更有效。沒有什麼比做好防曬更能保護肌膚的了。 --Hosting provided by SoundOn