Willow bark is where salicylic acid’s story began: the bark of Salix species carries salicin, the compound nineteenth-century chemists refined into salicylic acid and, eventually, into aspirin. In skincare the extract serves as a botanical companion to lab-made salicylic acid rather than a replacement for it.
How it works
Salicin itself is not an exfoliant — skin enzymes must convert it toward salicylate before it contributes, which happens slowly and gently. What the whole extract adds beyond salicin is a bundle of polyphenols and tannins with mild astringent, antioxidant and soothing activity. The practical effect in a formula is a soft assist to pore-clearing and surface smoothness with very little irritation of its own.
In formulation
Common in exfoliating toners, peels and blemish products, usually alongside true salicylic acid — the extract rounds the edges while the acid does the measurable keratolytic work. Claims that willow bark is a “natural BHA” overstate it; the conversion to active salicylate on skin is minor.
Worth knowing
Because its chemistry is salicylate chemistry, anyone with an aspirin (salicylate) allergy should avoid leave-on products containing willow bark — the same caution that applies to salicylic acid itself.
