You may have heard the term “hair porosity” and wondered what it means. Essentially, hair porosity is about your hair’s ability to absorb and retain moisture.

The porosity of your hair affects how well oils and moisture pass in and out of the outermost layer of your hair, known as the cuticle.

Here are the three types of hair porosities: 

  • Low porosity: Cuticles that are close together.

  • Medium porosity: Cuticles that are less tightly bound.

  • High porosity: Cuticles that are more widely spaced.

What does hair porosity mean?

To understand the concept of hair porosity, it helps to know a bit about the structure of your hair, which consists of three layers. These layers include:

  • The cuticle: This is the tough, protective outer layer of your hair that’s made up of smaller cuticles that overlap each other, similar to shingles on a roof.

  • The cortex: This is the thickest layer of your hair. It contains fibrous proteins and the pigment that gives your hair its color.

  • The medulla: This is the soft, central part of the hair shaft.

For your hair to stay healthy and hydrated, water, oils, and other moisturizing products need to be able to pass through the cuticle to get to the cortex.

What causes low or high hair porosity?

Blow drying, bleaching, straightening, overwashing, and using harsh products can all damage your hair over time. This can cause your hair cuticles to become raised and open, which may make it harder for your hair to retain moisture. 

Is there an easy way to test your hair porosity?

One of the easiest ways to test your hair porosity is by using a glass of water. Here’s how to do it:

  1. Shampoo and rinse your hair to remove any product buildup.

  2. Fill a glass with water.

  3. Once your hair is clean and dry, drop a single strand of your hair into the glass of water.

  4. Watch the strand to see if it sinks to the bottom of the glass or floats at the top.