Salicin

Salicin (a willow bark–derived beta-hydroxy-like precursor) is used as a keratolytic/anti-inflammatory exfoliating active, typically around ~0.1–2%, and can increase stinging and dryness in compromised barriers similarly to other exfoliants. Clinical and consumer experience show it is generally milder than salicylic acid but still capable of provoking irritation in eczema-prone or highly reactive skin, especially when layered with retinoids, acids, or benzoyl peroxide. Given its active, exfoliation-adjacent behavior and real-world cumulative irritation risk, a moderate score with patch testing is the safest assessment. Safety Notes: In commercial skincare, salicin (the defined beta-glucoside salicyl alcohol, distinct from generic “willow bark extract”) is typically used at very low levels (~0.01–0.2%) in gentle toners, essences, and daily moisturizers where it supports mild exfoliation/soothing without appreciable irritation. Higher-strength consumer leave-on acne/exfoliating serums and targeted treatments are commonly formulated around ~0.5–1.0% salicin, with a small number of specialty OTC products reaching about 2.0% as an upper end due to solubility, sensory/irritation limits, and the fact that many brands switch to salicylic acid for higher keratolytic strength. Rinse-off cleansers generally sit toward the lower half of the range because of short contact time, while the highest levels are observed in leave-on formats.