Thiamidol

Evidence by route

About this ingredient

Thiamidol (Isobutylamido Thiazolyl Resorcinol) is a synthetic depigmenting agent developed by Beiersdorf (Eucerin Anti-Pigment, Pigment Clarity brands). Acts via direct and reversible inhibition of human tyrosinase – the key enzyme of melanogenesis. According to Beiersdorf data, it inhibits tyrosinase 100 times more effectively than hydroquinone. Where applied. Serums and creams for hyperpigmentation, post-acne marks, melasma, post-inflammatory and sun pigmentation. Concentration in finished products – 0.2%. Evidence base. Beiersdorf clinical trials 2019–2021 showed pigment spot intensity reduction (by MASI index) of 30–50% over 12 weeks with 0.2% serum. The effect is comparable to azelaic acid 20% without irritation. Hydroquinone 2–4% is more effective short-term but is not allowed in EU OTC cosmetics and causes irritation, ochronosis. Safety. CIR/SCCS so far confirm safety at concentrations up to 0.2%. Irritation potential is low; non-comedogenic. Systemic absorption is minimal. Pregnancy and lactation – use with caution. Direct data are limited, but 0.2% concentration and minimal absorption make risk low. Alternatives with stronger evidence in pregnancy – azelaic acid 10–20%, niacinamide 5%, vitamin C. What to combine with. Sunscreen SPF 50+ (mandatory), niacinamide, retinaldehyde 0.05%, low-concentration AHA acids. Full effect – at 12 weeks.

Tolerability and safety

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