How does humidity typically affect hair?

Humidity typically affects hair by promoting frizz. This occurs because high humidity levels increase the moisture content in the air, which can lead to the absorption of water by the hair strands. When hair absorbs this moisture, it swells and causes the cuticle, the outer layer of the hair, to lift. This lifting creates a rough surface, which can result in the hair sticking out or becoming unmanageable, manifesting as frizz.

While humidity can enhance curl definition for some hair types, the primary and more common effect observed is the increase in frizz due to the hair's response to excess moisture. Understanding this reaction is important for hairstyling and product selection, as individuals may seek specific products designed to combat frizz in humid conditions.