Menthol is a partial antagonist of Substance P at the nerve terminal. As such, it functions as a counter-irritant and helps reduce discomfort. A clinical study that evaluated the application of menthol following capsaicin (the hot substance in cayenne and other peppers), irritation from the capsaicin was significantly reduced. Menthol helps itching without causing any lack of sensation in the nerve, and menthol may also assist in the delivery of other actives within the formula. Although unlikely, a rare individual might not tolerate menthol.