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Topical OTC use. Benzoyl peroxide is used at 2.5-10% in gels, creams, and washes, applied to acne-prone areas once or twice daily; lower strengths (2.5-5%) are usually as effective as 10% with less irritation. There is no oral or systemic dose — it is not ingested. It is often combined with a retinoid (e.g. adapalene) for greater effect. This library does not provide an ingestion protocol.

Any time

Leave-on gel/cream (2.5-5%) or a fixed combination with a retinoid

Topical cosmetic only. Niacinamide is typically formulated at 2-5% in leave-on serums, creams, or gels and applied to clean skin once or twice daily (AM and/or PM). It layers well under sunscreen and with most other actives. There is no oral, injectable, or systemic dose in this cosmetic context — it is not ingested here. This library does not provide an ingestion protocol.

Any time

Leave-on topical serum or cream (2-5% niacinamide)

• For topical (skin) use only — not for ingestion, not for injection
• Known allergy/sensitivity to benzoyl peroxide (true allergic contact dermatitis is uncommon but possible)
• Application to broken, severely inflamed, or sunburned skin until healed

• Topical retinoids degraded by oxidation (some tretinoin formulations)
• Other irritating actives (acids, other retinoids)

• For topical (skin) use only — not for ingestion, not for injection (in this cosmetic context)
• Known allergy or sensitivity to niacinamide or formulation excipients
• Application to broken, irritated, or compromised skin until healed

• Pure ascorbic acid (vitamin C) at low pH
• Strong leave-on exfoliating actives (AHAs/BHAs, retinoids)