High-porosity hair absorbs moisture instantly but loses it just as fast, leading to chronic dryness and frizz.

Hair porosity is a biological measurement of how easily the hair shaft can absorb and retain moisture. The hair cuticle consists of overlapping scales made of keratin that protect the inner cortex. In high-porosity hair, these scales are lifted or missing due to genetics, heat damage, or chemical treatments like bleaching. This structural state is often measured using the 'float test' or more accurately through gas sorption or scanning electron microscopy (SEM).Research published in the International Journal of Cosmetic Science highlights that damaged cuticles increase the hair's surface area, making it highly hydrophilic. While the hair absorbs water rapidly, it lacks the barrier necessary to prevent evaporation, a process called transepidermal water loss when applied to skin but referred to as desiccation in hair fibers. This leads to a cycle of swelling and shrinking known as hygral fatigue, which weakens the hair fiber over time.To combat this, trichologists recommend the L.O.C. (Liquid, Oil, Cream) method to create an artificial barrier. Heavy lipids like shea butter or coconut oil have large molecular structures that can physically plug the gaps in the cuticle. Studies from brands like Redken and L'Oréal have shown that acidic pH products can also help by chemically forcing the cuticle scales to lay flatter. This helps maintain the hair's internal moisture balance and reduces the friction that causes frizz.