What it is
Active ingredients: adapalene 0.1% with benzoyl peroxide 2.5%, as a fixed
combination on the acne pathway. In the EU this
combination is marketed under brand names including Epiduo and Acniduo.
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
Different targets
The retinoid works on the microcomedone; benzoyl peroxide works on inflammation and bacterial load. Comedonal and inflammatory acne rarely occur in isolation, so covering both is usually the sensible move.
Faster visible effect
The retinoid component is slow. The benzoyl peroxide component acts on inflammatory lesions sooner, which makes the first weeks less discouraging.
No antibiotic involved
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.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 covers the
distinction.
Realistic timelines
1
Weeks 1–4
Retinisation. Dryness, flaking, tightness, and often an apparent worsening. Reduced frequency and a bland moisturiser are the usual management.
2
Weeks 4–8
Irritation settles as tolerance develops. The rate of new lesions typically starts to fall.
3
Weeks 8–12
The fair point of assessment. Twelve weeks of consistent use is the usual minimum before judging a topical acne treatment.
4
Beyond 12 weeks
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 covers what the consultation fee includes.Related reading
- Acne
- Benzoyl peroxide · azelaic acid · topical clindamycin
- Tretinoin — the reference retinoid, used on the anti-ageing pathway
- How to apply a prescription topical
- Side effects of dermatology topicals
- Safety and eligibility
Start a consultation
Acne 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 and
how the review works.