Humectants are non-oil based ingredients that attract moisture from the atmosphere. They pull in and hold water to keep hair, or skin, moist and soft. While hydrating, they also slow down the evaporation of liquid and can therefore be frequently found in conditioners meant for dry or damaged hair. Humectants take many common forms from natural (honey is a well known natural humectant) to synthetic (for propylene glycol). They and are particularly effective in dry climates.

Much like humectants help moisturize in dry climates, anti-humectants are rather useful in humid environments. They add shine and definition but help to tame hair since they naturally repel unwanted moisture from the hair while preventing frizziness and flyaways. It is mostly used in styling, anti-frizz serums for hair which curls when there is moisture in the atmosphere.