Oakmoss

Oakmoss is a lichen (Evernia prunastri) that grows on oak bark, extracted into a resin that smells of damp forest, leather, and a briny, iodine-like richness. It's the defining base note of the chypre family — Mitsouko, Yvresse, and Aromatics Elixir all rest on it. Oakmoss has been heavily restricted by IFRA due to allergenic atranorin and chloroatranorin, and modern 'oakmoss' is often treemoss, evernyl, or synthetic reconstructions. The regulation is why modern chypres smell softer and less 'wet-leather' than the classics.