Menthol, known for its "cooling" effect, is often irritating to skin in high amounts.

Derived from peppermint, menthol can have the same sensitizing effect as peppermint on skin. Despite its documented ability to sensitize skin, menthol is included in a surprisingly large number of products. Unfortunately, the cooling, refreshing sensation menthol causes is direct evidence that your skin is being sensitized, not soothed.