{"id":310,"date":"2026-10-01T00:07:02","date_gmt":"2026-09-30T23:07:02","guid":{"rendered":"https:\/\/novameds.health\/au\/tretinoin-vs-retinol\/"},"modified":"2026-10-01T23:06:24","modified_gmt":"2026-10-01T13:06:24","slug":"tretinoin-vs-retinol","status":"publish","type":"post","link":"https:\/\/novameds.health\/au\/knowledge-hub\/tretinoin-vs-retinol\/","title":{"rendered":"Tretinoin vs Retinol: Mechanisms, Conversion and Anti-Ageing Evidence"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">In dermatological science and aesthetic medicine, retinoids (derivatives of Vitamin A) represent the most extensively validated, evidence-based topical compounds for treating acne vulgaris, reversing ultraviolet-induced photoageing, and stimulating dermal collagen synthesis.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">However, consumers and patients frequently encounter confusion between over-the-counter <strong>retinol<\/strong> and prescription <strong><a href=\"https:\/\/novameds.health\/au\/product\/tretinoin\/\">tretinoin<\/a><\/strong> (all-trans retinoic acid, historically marketed as Retin-A). While both belong to the broad retinoid family, they are fundamentally distinct in their chemical structure, biological potency, cellular conversion steps, and regulatory classifications.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Tretinoin is a direct pharmaceutical hormone-like ligand that binds directly to nuclear receptors, whereas retinol is a cosmetic precursor that requires multi-step metabolic conversion within keratinocytes.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This article reviews the cellular biology of the retinoid conversion cascade, compares histological and clinical anti-ageing trial outcomes, explores titration concentrations, and details evidence-based protocols to manage retinoid dermatitis (&#8220;the purge&#8221; and peeling).<\/p>\n\n\n\n<aside class=\"wp-block-group nm-takeaways is-layout-flow wp-block-group-is-layout-flow\">\n<h2 class=\"wp-block-heading\">Key takeaways<\/h2>\n\n\n\n<ul class=\"wp-block-list\"><li><strong>Direct Ligand vs Metabolic Precursor:<\/strong> Tretinoin is pure <strong>all-trans retinoic acid (ATRA)<\/strong>, which immediately binds to nuclear retinoic acid receptors (RARs) without requiring enzymatic conversion. Retinol must undergo a two-step intracellular oxidation (Retinol \u2192 Retinaldehyde \u2192 Retinoic Acid) inside skin cells.<\/li><li><strong>Magnitude of Potency:<\/strong> Pharmacological studies demonstrate that tretinoin is approximately <strong>20 times more potent<\/strong> by weight than cosmetic retinol at equivalent concentrations, due to incomplete enzymatic conversion and metabolic loss in the skin.<\/li><li><strong>Gold-Standard Histological Validation:<\/strong> Decades of punch-biopsy clinical trials confirm that topical tretinoin thickens the viable epidermis, accelerates stratum corneum cell turnover, compacts dead corneocytes, stimulates Type I and Type III pro-collagen synthesis in the papillary dermis, and disperses melanin granules.<\/li><li><strong>The &#8220;Retinoid Dermatitis&#8221; Hurdle:<\/strong> Tretinoin&#8217;s higher potency carries significantly greater local adverse effects upon initiation: erythema, peeling, stinging, dryness, and transient acne flare-ups (&#8220;purging&#8221;). Retinol is gentler and better tolerated by sensitive skin, though it produces slower, less dramatic structural changes.<\/li><li><strong>Regulatory Status:<\/strong> Tretinoin is a <strong>prescription-only medicine (POM)<\/strong> in the United Kingdom, United States, and European Union. Retinol is classified as an <strong>over-the-counter cosmetic ingredient<\/strong>, subject to cosmetic safety limits (e.g. European Commission SCCS concentration caps of 0.3% in facial products).<\/li><\/ul>\n<\/aside>\n\n\n\n<nav class=\"wp-block-group nm-toc is-layout-flow wp-block-group-is-layout-flow\" aria-label=\"Contents\">\n<h2 class=\"wp-block-heading\">Contents<\/h2>\n\n\n\n<ol><li><a href=\"#at-a-glance-molecular-and-clinical-comparison\">At a Glance: Molecular and Clinical Comparison<\/a><\/li><li><a href=\"#the-retinoid-conversion-cascade-in-skin-cells\">The Retinoid Conversion Cascade in Skin Cells<\/a><\/li><li><a href=\"#nuclear-mechanism-how-retinoic-acid-reprograms-gene-expression\">Nuclear Mechanism: How Retinoic Acid Reprograms Gene Expression<\/a><\/li><li><a href=\"#clinical-trial-evidence-for-photoageing-and-collagen-synthesis\">Clinical Trial Evidence for Photoageing and Collagen Synthesis<\/a><\/li><li><a href=\"#tretinoin-concentrations-0025-005-vs-01\">Tretinoin Concentrations: 0.025%, 0.05% vs 0.1%<\/a><\/li><li><a href=\"#managing-retinoid-dermatitis-purging-and-the-sandwich-method\">Managing Retinoid Dermatitis, Purging and the &#8220;Sandwich Method&#8221;<\/a><\/li><li><a href=\"#regulatory-landscape-prescription-vs-cosmetic-restrictions\">Regulatory Landscape: Prescription vs Cosmetic Restrictions<\/a><\/li><li><a href=\"#frequently-asked-questions\">Frequently Asked Questions<\/a><\/li><li><a href=\"#references\">Scientific references<\/a><\/li><\/ol>\n<\/nav>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"at-a-glance-molecular-and-clinical-comparison\">At a Glance: Molecular and Clinical Comparison<\/h2>\n\n\n\n<figure class=\"wp-block-table nm-table\"><table><thead><tr><th>Characteristic<\/th><th>Tretinoin (Retin-A, Ketrel, Treclin)<\/th><th>Retinol (Cosmetic Over-the-Counter)<\/th><\/tr><\/thead><tbody><tr><td><strong>Chemical Identity<\/strong><\/td><td>All-trans retinoic acid (ATRA)<\/td><td>Pure Vitamin A alcohol<\/td><\/tr><tr><td><strong>Active Biological Form?<\/strong><\/td><td><strong>Yes.<\/strong> Directly active at nuclear receptors<\/td><td><strong>No.<\/strong> Inactive precursor requiring oxidation<\/td><\/tr><tr><td><strong>Enzymatic Conversion<\/strong><\/td><td><strong>0 steps<\/strong> (Immediate biological action)<\/td><td><strong>2 enzymatic steps<\/strong> (Alcohol Dehydrogenase + RALDH)<\/td><\/tr><tr><td><strong>Relative Biological Potency<\/strong><\/td><td><strong>1.0 (Baseline Reference)<\/strong><\/td><td><strong>~0.05 (roughly 20x less potent)<\/strong><\/td><\/tr><tr><td><strong>Typical Concentrations<\/strong><\/td><td><strong>0.025%, 0.05%, 0.1%<\/strong><\/td><td><strong>0.1%, 0.3%, 0.5%, 1.0%<\/strong><\/td><\/tr><tr><td><strong>Time to Visible Clinical Results<\/strong><\/td><td><strong>6 to 12 weeks<\/strong><\/td><td><strong>12 to 24 weeks<\/strong><\/td><\/tr><tr><td><strong>Initial Irritation Risk<\/strong><\/td><td>High (erythema, desquamation, stinging)<\/td><td>Low to moderate<\/td><\/tr><tr><td><strong>Acne Clearance Indication<\/strong><\/td><td>Officially approved prescription indication<\/td><td>Not an approved drug treatment for acne<\/td><\/tr><tr><td><strong>Legal Classification<\/strong><\/td><td>Prescription-Only Medicine (POM)<\/td><td>Over-the-counter cosmetic<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"the-retinoid-conversion-cascade-in-skin-cells\">The Retinoid Conversion Cascade in Skin Cells<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">To exert any physiological effect on the skin, all topical Vitamin A derivatives must ultimately be converted into a single bioactive molecule: <strong>all-trans retinoic acid<\/strong>:<\/p>\n\n\n\n<pre class=\"wp-block-preformatted nm-diagram\">                       The Retinoid Metabolic Pathway\n                                      \u2502\n               Retinyl Esters (Palmitate, Propionate, Acetate)\n                                      \u2502  [ Esterases ]\n                                      \u25bc\n                                   Retinol\n                                      \u2502  [ Alcohol Dehydrogenase (ADH) ]\n                                      \u25bc\n                               Retinaldehyde\n                                      \u2502  [ Retinaldehyde Dehydrogenase (RALDH) ]\n                                      \u25bc\n                       ALL-TRANS RETINOIC ACID (TRETINOIN)\n                                      \u2502\n              \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2534\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510\n              \u25bc                                               \u25bc\nNuclear Retinoic Acid Receptors (RAR)         Retinoid X Receptors (RXR)\n\u2022 Downregulates MMP collagen breakdown       \u2022 Accelerates epidermal cell turnover\n\u2022 Upregulates Type I &amp; III collagen genes     \u2022 Compacts stratum corneum<\/pre>\n\n\n\n<ol class=\"wp-block-list\"><li><strong>Retinyl Esters:<\/strong> The weakest cosmetic derivatives (retinyl palmitate, retinyl propionate). They require three enzymatic steps, resulting in negligible retinoic acid conversion and minimal clinical efficacy.<\/li><li><strong>Retinol:<\/strong> Requires two rate-limiting enzymatic steps:<ul class=\"wp-block-list\"><li>First, cytosolic <strong>alcohol dehydrogenases (ADHs)<\/strong> oxidize retinol into retinaldehyde.<\/li><li>Second, <strong>retinaldehyde dehydrogenases (RALDHs)<\/strong> oxidize retinaldehyde into retinoic acid.<\/li><li><em>The Metabolic Bottleneck:<\/em> Keratinocytes strictly regulate these enzymatic steps. Only a small fraction (estimated at 2% to 6%) of topically applied retinol is converted into active retinoic acid; the remainder is esterified and stored or cleared.<\/li><\/ul><\/li><li><strong>Tretinoin:<\/strong> Skips the enzymatic bottleneck entirely. Because it is already pure all-trans retinoic acid, it enters the cell and translocates directly into the cell nucleus, delivering 100% molecular bioavailability to nuclear receptors.<\/li><\/ol>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"nuclear-mechanism-how-retinoic-acid-reprograms-gene-expression\">Nuclear Mechanism: How Retinoic Acid Reprograms Gene Expression<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Tretinoin operates like a steroid hormone. Upon diffusing through the plasma membrane, it is bound by cellular retinoic acid-binding proteins (CRABP I and II) and transported into the nucleus:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li><strong>RAR and RXR Heterodimers:<\/strong> Tretinoin binds specifically to <strong>retinoic acid receptors (RAR-\u03b1, RAR-\u03b2, RAR-\u03b3)<\/strong>, which form heterodimers with <strong>retinoid X receptors (RXRs)<\/strong>.<\/li><li><strong>Direct Genomic Transcription:<\/strong> These heterodimers bind to specific DNA sequences known as <strong>Retinoic Acid Response Elements (RAREs)<\/strong> in the promoter regions of target genes, switching on transcription of genes responsible for:<ul class=\"wp-block-list\"><li><strong>Epidermal Renewal:<\/strong> Accelerating basal keratinocyte proliferation and shedding of hyperkeratinized stratum corneum cells (preventing the formation of microcomedones in acne).<\/li><li><strong>Dermal Extracellular Matrix Biosynthesis:<\/strong> Activating dermal fibroblasts to produce pro-collagen Type I and Type III, tropoelastin, and hyaluronic acid.<\/li><li><strong>MMP Inhibition (Anti-Catabolic):<\/strong> Tretinoin directly suppresses <strong>activator protein-1 (AP-1)<\/strong>, a transcription factor induced by UV radiation that triggers matrix metalloproteinases (MMP-1 collagenase, MMP-3 stromelysin, MMP-9 gelatinase). By shutting down AP-1, tretinoin halts the enzymatic breakdown of existing dermal collagen.<\/li><\/ul><\/li><\/ul>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"clinical-trial-evidence-for-photoageing-and-collagen-synthesis\">Clinical Trial Evidence for Photoageing and Collagen Synthesis<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The clinical validation of tretinoin is unmatched in dermatology, initiated by landmark trials by Dr. Albert Kligman and Dr. John Voorhees in the 1980s and 1990s:<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"1-the-voorhees-double-blind-histological-trials\">1. The Voorhees Double-Blind Histological Trials<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">In landmark randomized trials published in <em>JAMA<\/em> and the <em>New England Journal of Medicine<\/em>:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Patients applied 0.05% tretinoin cream or vehicle to photodamaged forearms and faces over 4 to 12 months.<\/li><li><strong>Biopsy Findings:<\/strong> Full-thickness skin biopsies revealed that tretinoin produced an <strong>80% increase in collagen-anchoring fibril density<\/strong> in the papillary dermis.<\/li><li>Type I pro-collagen mRNA increased by <strong>multiple-fold<\/strong>, while epidermal thickness increased by an average of <strong>30%<\/strong>, reversing the epidermal atrophy characteristic of intrinsic and actinic ageing.<\/li><\/ul>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"2-clinical-outcomes-in-wrinkles-and-hyperpigmentation\">2. Clinical Outcomes in Wrinkles and Hyperpigmentation<\/h3>\n\n\n\n<ul class=\"wp-block-list\"><li><strong>Fine Lines and Wrinkles:<\/strong> Significant clinical smoothing of periorbital and perioral fine lines occurred by month 3, with progressive improvements in deeper wrinkles observed through months 6 to 12.<\/li><li><strong>Melanin Dispersion:<\/strong> Tretinoin accelerated the turnover of melanin-laden keratinocytes, dispersing irregular pigment clumps and fading solar lentigines (age spots) far more rapidly than retinol.<\/li><\/ul>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"tretinoin-concentrations-0025-005-vs-01\">Tretinoin Concentrations: 0.025%, 0.05% vs 0.1%<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Prescription tretinoin is standardly formulated in three distinct concentrations:<\/p>\n\n\n\n<figure class=\"wp-block-table nm-table\"><table><thead><tr><th>Concentration<\/th><th>Primary Clinical Indications<\/th><th>Efficacy Profile<\/th><th>Irritation Potential<\/th><\/tr><\/thead><tbody><tr><td><strong>0.025%<\/strong><\/td><td>Initiation phase, sensitive skin, anti-ageing maintenance<\/td><td>Excellent long-term collagen synthesis; identical to 0.1% at 12 months<\/td><td>Lowest irritation; ideal for beginner tolerance<\/td><\/tr><tr><td><strong>0.05%<\/strong><\/td><td>Standard therapeutic concentration for photoageing &amp; mild acne<\/td><td>Accelerated dermal remodelling and wrinkle reduction<\/td><td>Moderate irritation; requires acclimatisation<\/td><\/tr><tr><td><strong>0.1%<\/strong><\/td><td>Severe cystic acne, severe hyperkeratosis, thick oily skin<\/td><td>Fastest onset of acne comedolysis and hyperpigmentation fading<\/td><td>Highest irritation; significant risk of retinoid dermatitis<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\"><em>Crucial Dermatological Insight:<\/em> A landmark double-blind trial by Griffiths and colleagues (<em>Archives of Dermatology<\/em>) compared <strong>0.025% vs 0.1% tretinoin<\/strong> over 48 weeks. While 0.1% produced faster improvements at 12 weeks, by <strong>week 48 both concentrations achieved statistically identical improvements in histological collagen synthesis and wrinkle reduction<\/strong>, but 0.025% caused dramatically less irritation and peeling.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"managing-retinoid-dermatitis-purging-and-the-sandwich-method\">Managing Retinoid Dermatitis, Purging and the &#8220;Sandwich Method&#8221;<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The primary barrier to successful tretinoin therapy is <strong>retinoid dermatitis<\/strong>: acute erythema, barrier impairment, scaling, dryness, and transient inflammatory acne flare-ups (&#8220;the purge&#8221;).<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"why-purging-occurs\">Why &#8220;Purging&#8221; Occurs<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Tretinoin accelerates epidermal turnover, compressing a normal 28-day shedding cycle into 10 to 14 days. Sub-clinical microcomedones already forming deep within pores are rapidly propelled to the surface simultaneously, causing a temporary surge in visible breakouts during weeks 2 to 6. This is not an allergic reaction; it is a mechanical clearance of pre-existing microcomedones.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"the-evidence-based-initiation-protocol\">The Evidence-Based Initiation Protocol:<\/h3>\n\n\n\n<ol class=\"wp-block-list\"><li><strong>Low Frequency Titration:<\/strong><ul class=\"wp-block-list\"><li>Weeks 1\u20132: Apply twice weekly at night.<\/li><li>Weeks 3\u20134: Apply every other night.<\/li><li>Week 5 onwards: Increase to nightly application as tolerated.<\/li><\/ul><\/li><li><strong>The &#8220;Pea-Sized&#8221; Rule:<\/strong> Apply no more than a single pea-sized amount (~0.25 g) for the entire face. Using excess product increases barrier toxicity without accelerating collagen synthesis.<\/li><li><strong>The &#8220;Sandwich Method&#8221; for Sensitive Skin:<\/strong><ul class=\"wp-block-list\"><li>Step 1: Apply a light layer of non-comedogenic ceramide-rich moisturizer.<\/li><li>Step 2: Allow to dry for 10 minutes, then apply the pea-sized tretinoin.<\/li><li>Step 3: Layer a richer barrier cream over the top.<\/li><li><em>Clinical Note:<\/em> The sandwich method buffers the rate of stratum corneum penetration, markedly reducing trans-epidermal water loss (TEWL) and erythema without abolishing nuclear gene transcription.<\/li><\/ul><\/li><li><strong>Mandatory Sunscreen:<\/strong> Tretinoin thins the outer non-viable stratum corneum, increasing susceptibility to UV erythema. Daily broad-spectrum SPF 30\u201350 is medically mandatory.<\/li><\/ol>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"regulatory-landscape-prescription-vs-cosmetic-restrictions\">Regulatory Landscape: Prescription vs Cosmetic Restrictions<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The international regulatory standing of retinoids reflects their pharmacological potency:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li><strong>Tretinoin (Prescription-Only):<\/strong> In the UK (MHRA), United States (FDA), and European Union (EMA), tretinoin is strictly a prescription medicinal product. It cannot be legally sold in cosmetic over-the-counter creams.<\/li><li><strong>European Cosmetic Retinol Caps (2024\u20132026):<\/strong> In 2024, the European Commission, following recommendations from the Scientific Committee on Consumer Safety (SCCS), enacted regulations restricting over-the-counter retinol, retinyl acetate, and retinyl palmitate to a maximum concentration of <strong>0.3% in facial cosmetics<\/strong> (and 0.05% in body lotions) due to concerns regarding cumulative dietary and topical Vitamin A exposure.<\/li><li><strong>Pregnancy Warning:<\/strong> All retinoids\u2014both prescription tretinoin and cosmetic retinol\u2014are <strong>strictly contraindicated during pregnancy and breastfeeding<\/strong> due to the theoretical risk of teratogenicity.<\/li><\/ul>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"frequently-asked-questions\">Frequently Asked Questions<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"can-i-use-retinol-around-my-eyes-but-tretinoin-on-my-face\">Can I use retinol around my eyes, but tretinoin on my face?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Yes. The periorbital skin is approximately one-third the thickness of facial skin and contains fewer sebaceous glands, making it exceptionally vulnerable to retinoid dermatitis. Many patients use a gentle 0.1%\u20130.3% encapsulated retinol eye cream for crows&#8217; feet while applying prescription 0.025% tretinoin to the rest of the face.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"does-tretinoin-thin-the-skin-over-time\">Does tretinoin thin the skin over time?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">This is a persistent myth. Tretinoin thins only the dead, outermost stratum corneum (removing dull, dead corneocytes). In the deeper, living layers, tretinoin <strong>thickens the viable epidermis and dramatically increases the depth and density of the dermal collagen matrix<\/strong>, resulting in thicker, more structurally resilient skin over years of continuous use.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"can-i-use-tretinoin-alongside-chemical-exfoliants-aha--bha\">Can I use tretinoin alongside chemical exfoliants (AHA \/ BHA)?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">During the first 3 to 6 months of initiating tretinoin, all alpha-hydroxy acids (glycolic, lactic) and beta-hydroxy acids (salicylic) should be paused. Combining chemical peels with retinoid-induced cellular turnover almost universally precipitates severe cutaneous barrier breakdown, contact dermatitis, and prolonged post-inflammatory hyperpigmentation (PIH).<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Related reading: <a href=\"https:\/\/novameds.health\/au\/knowledge-hub\/ghk-cu-evidence-review\/\">GHK-Cu Copper Peptide: Evidence for Skin Remodelling and Wound Repair<\/a> \u00b7 <a href=\"https:\/\/novameds.health\/au\/knowledge-hub\/isotretinoin-evidence-and-safety\/\">Isotretinoin (Roaccutane): Evidence, Safety, Teratogenicity and Monitoring<\/a> \u00b7 <a href=\"https:\/\/novameds.health\/au\/knowledge-hub\/finasteride-vs-minoxidil\/\">Finasteride vs Minoxidil: Different Approaches to Hair Loss<\/a><\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"references\">Scientific references<\/h2>\n\n\n\n<ol class=\"nm-refs\"><li id=\"ref-1\"><strong>Weiss JS, et al.<\/strong> <em>Topical tretinoin improves photoaged skin. A double-blind vehicle-controlled study.<\/em> JAMA. 1988;259(4):527-532. <a href=\"https:\/\/pubmed.ncbi.nlm.nih.gov\/3336176\/\">PubMed PMID: 3336176<\/a><\/li><li id=\"ref-2\"><strong>Kligman AM.<\/strong> <em>The treatment of photoaged skin with topical tretinoin.<\/em> International Journal of Dermatology. 1989;28(9):608-610.<\/li><li id=\"ref-3\"><strong>Fisher GJ, et al.<\/strong> <em>Molecular mechanisms of photoaging and its prevention by retinoic acid: ultraviolet irradiation induces MAP kinase-mediated AP-1 activation that represses collagen synthesis.<\/em> Journal of Clinical Investigation. 1996;97(3):681-689. <a href=\"https:\/\/pubmed.ncbi.nlm.nih.gov\/8609223\/\">PubMed PMID: 8609223<\/a><\/li><li id=\"ref-4\"><strong>Griffiths CE, et al.<\/strong> <em>Two concentrations of topical tretinoin (retinoic acid) cause similar improvement of photoaging but different degrees of irritation: a double-blind, vehicle-controlled comparison of 0.1% and 0.025% tretinoin creams.<\/em> Archives of Dermatology. 1995;131(9):1037-1044. <a href=\"https:\/\/pubmed.ncbi.nlm.nih.gov\/7661603\/\">PubMed PMID: 7661603<\/a><\/li><li id=\"ref-5\"><strong>Kang S, et al.<\/strong> <em>Application of retinol to human skin in vivo induces epidermal hyperplasia and cellular retinoid binding proteins characteristics of retinoic acid but with less irritation.<\/em> Journal of Investigative Dermatology. 1995;105(4):549-556. <a href=\"https:\/\/pubmed.ncbi.nlm.nih.gov\/7561157\/\">PubMed PMID: 7561157<\/a><\/li><\/ol>\n\n\n\n<p class=\"nm-article-note wp-block-paragraph\">This article is educational and does not constitute personalised treatment advice. Treatment decisions depend on individual circumstances and professional assessment.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Tretinoin is pure all-trans retinoic acid; retinol must undergo a two-step intracellular conversion. We compare their molecular pharmacology, clinical anti-ageing efficacy, irritation management and prescribing status.<\/p>\n","protected":false},"author":0,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[174],"tags":[202],"class_list":["post-310","post","type-post","status-publish","format-standard","hentry","category-comparisons","tag-tretinoin"],"_links":{"self":[{"href":"https:\/\/novameds.health\/au\/wp-json\/wp\/v2\/posts\/310","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/novameds.health\/au\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/novameds.health\/au\/wp-json\/wp\/v2\/types\/post"}],"replies":[{"embeddable":true,"href":"https:\/\/novameds.health\/au\/wp-json\/wp\/v2\/comments?post=310"}],"version-history":[{"count":3,"href":"https:\/\/novameds.health\/au\/wp-json\/wp\/v2\/posts\/310\/revisions"}],"predecessor-version":[{"id":440,"href":"https:\/\/novameds.health\/au\/wp-json\/wp\/v2\/posts\/310\/revisions\/440"}],"wp:attachment":[{"href":"https:\/\/novameds.health\/au\/wp-json\/wp\/v2\/media?parent=310"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/novameds.health\/au\/wp-json\/wp\/v2\/categories?post=310"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/novameds.health\/au\/wp-json\/wp\/v2\/tags?post=310"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}