> ## Documentation Index > Fetch the complete documentation index at: https://docs.hi-doctor.ai/llms.txt > Use this file to discover all available pages before exploring further. # Adapalene — a third-generation topical retinoid > Adapalene 0.1% paired with benzoyl peroxide 2.5% is a mainstay of inflammatory acne. How the retinoid works, why the pairing exists, and the pregnancy rule. Adapalene is a synthetic naphthoic acid derivative that behaves as a retinoid — a third-generation one, designed to keep the useful receptor activity of tretinoin while being more chemically stable and less irritating. On this service it is prescribed in a fixed combination with benzoyl peroxide. ## What it is Active ingredients: **adapalene 0.1% with benzoyl peroxide 2.5%**, as a fixed combination on the [acne](/library/conditions/acne) pathway. In the EU this combination is marketed under brand names including Epiduo and Acniduo. **Pregnancy.** Topical retinoids, adapalene included, are not used in pregnancy, and their use while trying to conceive or breastfeeding is avoided. The pregnancy step in the acne questionnaire is a hard gate for exactly this reason. Anyone who could become pregnant should expect the reviewing doctor to ask about contraception before issuing a retinoid, and the decision is theirs to make. ## How it works Adapalene binds selectively to retinoic acid receptor subtypes in the nucleus of follicular keratinocytes. Through that binding it normalises the differentiation and cohesion of the cells lining the follicle, which reduces the formation of the microcomedone — the precursor lesion every other acne lesion develops from. It also has an independent anti-inflammatory effect, inhibiting the chemotactic and oxidative responses of polymorphonuclear leucocytes. Acting on the microcomedone is what distinguishes a retinoid from an anti-inflammatory or an antibacterial. It treats lesions that have not appeared yet, which is why the visible benefit is delayed and why the treatment is applied to the whole affected area rather than to individual spots. Adapalene is more photostable than tretinoin and less prone to oxidative degradation, which is what makes a fixed combination with benzoyl peroxide — a strong oxidiser — chemically viable. ## Why it is combined with benzoyl peroxide The retinoid works on the microcomedone; [benzoyl peroxide](/library/medicines/benzoyl-peroxide) works on inflammation and bacterial load. Comedonal and inflammatory acne rarely occur in isolation, so covering both is usually the sensible move. The retinoid component is slow. The benzoyl peroxide component acts on inflammatory lesions sooner, which makes the first weeks less discouraging. Neither component selects for bacterial resistance, unlike a topical antibiotic. That matters for a chronic condition treated over months. ## What has been reported The combination is more irritating than either component alone, and almost all of the reported effects are local. | Reported effect | Character | | ---------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------- | | Dryness, scaling, peeling | Very common in the first weeks; the defining feature of the retinisation phase | | Burning or stinging on application | Common early, usually settles with continued use | | Erythema and irritation | Common; disproportionate or spreading redness is a reason to stop and seek advice | | Photosensitivity | Retinoids increase sensitivity to ultraviolet light. Daily broad-spectrum protection is part of the treatment | | Bleaching of fabric and hair | Caused by the benzoyl peroxide component, not the retinoid — it is a chemical effect on dye, and it is permanent | | Contact allergy | Uncommon; a true allergic contact dermatitis to benzoyl peroxide is distinguishable from ordinary irritation by its spread and its itch | The initial worsening people describe as a "purge" is real. A retinoid accelerates the maturation of lesions already forming beneath the surface, so more of them surface at once early on. It is different from a treatment failure, which looks like new lesions still appearing at the same rate after eight to twelve weeks. The [side-effects guide](/library/guides/side-effects-dermatology) covers the distinction. ## Realistic timelines Retinisation. Dryness, flaking, tightness, and often an apparent worsening. Reduced frequency and a bland moisturiser are the usual management. Irritation settles as tolerance develops. The rate of new lesions typically starts to fall. The fair point of assessment. Twelve weeks of consistent use is the usual minimum before judging a topical acne treatment. Maintenance, usually with the retinoid at a reduced frequency, is what prevents the microcomedone reforming. Stopping when the skin looks clear is the most common cause of relapse. ## Who it is not suitable for Anyone who is pregnant, trying to conceive or breastfeeding. Anyone with known hypersensitivity to adapalene, to benzoyl peroxide or to an excipient. Broken, eczematous or sunburnt skin, where a retinoid is not applied. Beyond those, suitability is a judgement the reviewing doctor makes from the questionnaire — and severe, nodular, cystic or scarring acne is referred to in-person care rather than treated topically. ## How Hi-Doctor handles it The review is fully asynchronous — no video call, no telephone consultation. You complete the acne questionnaire, upload a photograph, and a registered doctor grades the case and decides. A prescription is never guaranteed, and if one is not issued the consultation fee is refunded in full. The medicine is dispensed and paid for at a pharmacy of your choosing; the [pricing page](/essentials/pricing) covers what the consultation fee includes. ## Related reading * [Acne](/library/conditions/acne) * [Benzoyl peroxide](/library/medicines/benzoyl-peroxide) · [azelaic acid](/library/medicines/azelaic-acid) · [topical clindamycin](/library/medicines/clindamycin-topical) * [Tretinoin](/library/medicines/tretinoin) — the reference retinoid, used on the anti-ageing pathway * [How to apply a prescription topical](/library/guides/how-to-apply-topicals) * [Side effects of dermatology topicals](/library/guides/side-effects-dermatology) * [Safety and eligibility](/essentials/safety) ## Start a consultation Answer the acne questionnaire, upload your photos, and a registered doctor reviews the case. They decide whether a topical treatment is appropriate and which one — declining is a normal outcome. See [what it costs](/essentials/pricing) and [how the review works](/essentials/how-it-works). This page is reference information, not medical advice and not a prescription. Whether a medicine is appropriate for you is decided by a registered doctor after reviewing your consultation.