A woman brushing her hair
Hair Porosity: What You Need To Know
Hair porosity is the hair's ability to absorb and hold moisture. While curly hair is naturally more porous, it often depends on genetic factors and the way you treat your hair.
Each strand of hair has layers, the outermost being the cuticle. Hair with low porosity has cuticles that are closely bound together, making it hard for moisture to get through.
With high porosity, the cuticles are more spread out. This type of hair can soak up products well but can't always hold them in because of how spread out the cuticles are.
In the middle of the spectrum, hair with cuticles that aren't too loosely or tightly bound is considered medium or normal porosity, which can retain moisture fairly well.
To test your own hair's porosity, comb out a few strands of hair and drop them in a glass of water. If they float, you have low porosity, and if it sinks, you have high porosity.
Also take note of how your hair reacts to products. High porosity hair soaks up product but doesn't retain it well, and low porosity hair has trouble absorbing products.
Hair trichologist Dr. Isfahan Chambers-Harris told Byrdie it’ll help to use a pre-shampoo oil on hair with low porosity. Then use a moisturizing shampoo that doesn’t strip hair.
High porosity hair needs a moisturizing shampoo with a repairing conditioner to help close the cuticles. Medium porosity hair needs deep conditioning products to remove impurities.