The underlying cause of frizz is usually a cuticle (the outer protective layer of the hair) that is raised/open instead of flats/sealed. The more the cuticle is raised or damaged (high porosity) the easier it is for moisture (and products) to travel in and out of the hair strand. This means moisture is absorbed easily but it cannot be retained or sealed into the hair.
Hair naturally demands moisture. Once dehydrated hair is dry, it starts to absorb ambient moisture from the air which swells up and frizzes out the hair strand. This is why humidity and frizz go hand in hand.
A raised or damaged cuticle layer results in dry, brittle, rough feeling hair. In contrast, when the cuticle layer stays flat and sealed, the hair is soft, smooth, shiny, healthy, and can retain moisture.
The science of frizz can be complex but the solution doesn’t have to be. The right knowledge, products, and techniques can help you restore moisture levels, lock out humidity, and smooth the outer protective cuticle layers for soft, shiny, and frizz-free hair.