What Is Hair Porosity and Why Does It Matter?

Determining your hair's porosity could be the key to addressing some of your biggest hair frustrations.

When you hear the word “porous,” you probably picture your skin or a sponge, but you should also consider your hair, since all hair has porosity. Hair porosity refers to the hair’s ability to absorb and retain moisture—so low porosity hair has a lower ability to hold moisture, while high porosity hair is the opposite.

To clarify, the fact that hair is porous doesn’t mean your hair is covered in a bunch of tiny holes but, rather, “scales.” These “scales” are cells that overlap like rooftop tiles on the outermost layer of the hair shaft. On low-porosity hair, the cells are more flattened and compact, while on high-porosity hair, the cells are more open and porous.

It’s important to understand hair porosity since it can determine a lot about your hair, from how it interacts with products and how it dries to how it feels. Understanding your hair’s porosity could be the key to figuring out the reasons behind some of your main hair frustrations—and how to treat them.

How to determine your hair’s porosity:

There’s a commonly circulated hair porosity test that involves sticking a loose strand of hair into a glass of water. The idea behind the test is this: If the strand floats, it’s low porosity, if the strand sinks slowly, it’s medium porosity, and if the strand sinks quickly, it’s high porosity. While these results align with the different hair porosity levels, there are a few other factors that could make the results of this at-home test inaccurate and misleading. Factors like how much oil is on the hair or how dense the hair is could affect whether it floats or sinks.

So a better way to determine your hair’s porosity is to pay close attention to how your hair acts in different circumstances. Diane Stevens, a hairstylist and owner of Cole Stevens Salon in Washington, D.C., has observed the many characteristics of varying hair porosities over the years. For low-porosity hair, she says it takes a long time for the hair to get fully saturated with water, and it dries quickly. Stevens also notes that because low-porosity hair has a harder time absorbing moisture, this means that products tend to stay on top of the hair and can cause buildup on the scalp.

The characteristics of high-porosity hair are the reverse. Rather than struggling to soak up moisture, high-porosity hair can’t get enough. High-porosity hair will drink up water and moisture quickly, but after using moisturizing products, the hair may still feel dried out. Additionally, high-porosity hair is more prone to damage, and Stevens adds that it often lacks shine. When trying to color-treat hair, low-porosity will take color poorly and requires more work, while high-porosity hair quickly absorbs dye.

If you don’t experience any of the characteristics or issues associated with high- or low-porosity hair, that likely means that your hair is medium porosity. Medium-porosity hair often requires the least amount of maintenance since it allows moisture in, holds a balanced amount of it, and doesn’t suffer from as much dryness or buildup as high- and low-porosity hair.

How to care for low-porosity hair:

According to Stevens, the primary challenge with caring for low-porosity hair is tackling buildup. To combat it, she recommends incorporating a clarifying shampoo and a scalp exfoliator, like the Nioxin Scalp Recovery Purifying Exfoliator, into your routine to help break down anything that may be hanging behind on the scalp.

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Nioxin Scalp Recovery Purifying Exfoliator

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“Exfoliating is amazing for the scalp, and it will remove any excess sebum at the scalp area, which is great for curly girls,” Stevens says. “[Nioxin Scalp Recovery Purifying Exfoliator] is also a relaxing scalp scrub that feels amazing and mechanically gets rid of scalp flakes, debris, and dead skin cell buildup.”

To make sure the hair is still getting moisturized, Stevens recommends clarifying just at the roots, rather than from roots to ends, and then using a conditioner on the ends.

How to care for medium-porosity hair:

Medium-porosity hair might not require as much regular maintenance as low-porosity hair, but it’s still good to get it some extra love and attention from time to time. Occasional deep-conditioning treatments with protein, like SheaMoisture’s Manuka Honey & Yogurt Hydrate + Repair Protein Treatment, can benefit the hair. Just note that too much topical protein can make your hair more susceptible to damage, so only use it once a week.

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SheaMoisture Manuka Honey + Yogurt Hydrate + Repair Protein Treatment

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How to care for high-porosity hair:

Since high-porosity hair is prone to damage, Stevens recommends using a pH-balanced shampoo and conditioner as pH levels can play a big role in the health of the hair cuticle. “Highly porous hair needs something that is a little lower on a pH scale so that the cuticle can close,” Stevens says. Her favorite is the Wella Invigo Brilliance Shampoo and Conditioner, and she explains that in the salon, her clients can often see the improvement in their hair almost immediately.

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Wella Invigo Brilliance Shampoo

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To keep high-porosity hair protected and shiny, Stevens also recommends getting a professional gloss treatment every eight to 12 weeks to help close the cuticle layer and condition the hair.

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