Which porosity level indicates that hair is extremely damaged?

High porosity indicates that hair is extremely damaged because this level of porosity occurs when the hair cuticle is lifted or damaged, allowing moisture and other substances to easily enter and exit the hair shaft. This often results from over-processing hair, such as through chemical treatments like coloring or perming, excessive heat styling, and environmental factors. Hair with high porosity tends to absorb moisture quickly but can also lose it just as quickly, leading to dryness and brittleness.

Understanding the porosity of hair is crucial for determining appropriate hair care practices. High porosity hair needs more moisture and conditioning to help combat its tendency to be dry and brittle. This contrasts with low porosity hair, which has a tightly closed cuticle and typically resists moisture absorption, and medium porosity, which maintains a balanced state that allows for adequate moisture retention without excessive damage. Non-porous hair, while rare, generally does not allow any moisture in or out, indicating a healthy cuticle layer.