Figuring out your hair's porosity can help you find the best products for your strands' needs.

By Renee Cherry
July 15, 2020
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The word "porosity" might take you back to eighth-grade science class, but the term isn't just used in reference to sponges and rocks. It also gets thrown around a lot in the haircare world.

Understanding the porosity of your hair can give you a better idea of which products are best suited to your unique needs. Here's more on what hair porosity is, how to figure out if you have low-porosity or high-porosity hair, and how to care for either. (Related: 3 Hair Pros Share Their Low-Maintenance Hair Routines)

What Is Hair Porosity?

Simply put, "porosity is the hair's ability to absorb moisture and keep moisture in the strands," says Kari Williams, Ph.D., trichologist and celebrity hairstylist. Hair's porosity results from the structure of individual strands of hair. I'll explain...

The outermost protective layer of hair is called the cuticle, and it looks like a row of shingles on a roof. The cuticle acts as a gatekeeper, controlling how much moisture can penetrate the strand. If the so-called singles are more raised (or the cuticle is open), there are larger spaces—or pores—in between each, making it easier for moisture to both enter and escape. This is considered high-porosity hair. On the other hand, if your cuticle layer is tightly closed (read: fewer gaps or pores, if any), it's—as you probably guessed—harder for moisture to escape and enter and is considered low-porosity hair.

TL;DR—The more open the cuticle, the higher porosity hair; the more closed the cuticle, the lower porosity hair.

Types of Low- and High-Porosity Hair 

More often than not, curly hair is on the porous side, whereas straighter hair is more likely to be nonporous, says Williams. "The more bends and curves in the hair strand, the more porous it will be because those bends and curves in the hair strand create cracks that allow moisture to escape or prevent it from being sealed into the hair strand." That being said, it's also possible to have low-porosity curly hair or high-porosity straight hair. (Related: My Favorite New Curly Hair Product Is Made for Dudes)

It's not always a matter of whether you were born with curly or straight hair, though—how you treat your hair also plays a role in porosity. Dye or other chemical treatments can damage the cuticle, increasing hair's porosity. Even excessive brushing or styling can make hair more porous, according to research. (So, make sure you know how to brush your hair the right way, friend!)

How to Determine Your Hair Porosity

How can you determine if you have high-porosity hair, low-porosity hair, or something in between? Take a dry, clean strand (meaning, with no styling products on it) of your hair out of your head, put it into a cup of water, and see how long it takes to sink to the bottom. If it sinks straight away, you have high-porosity hair; if it sinks after a few seconds, you have medium-porosity hair, and if takes even longer to sink, you have low-porosity hair, says David Petrillo, cosmetic chemist and founder of Perfect Image. The more porous the strand, the faster it will absorb water, get heavy, and drop it ~low~ (aka sink).

While this ability to suck up moisture might seem like a good thing, especially when your hair is dry AF, it can also come with challenges. And the same is true for low-porosity hair as well. Point being: at either extreme, you can deal with difficulties when trying to keep your hair adequately hydrated. The good news? The proper products can help. Once you're aware of the porosity of your locks, you can modify your hair care routine to work in your favor. (Related: 5 Women with Different Hair Types Share Their Hair-Care Routines)

How to Treat Low-Porosity Hair

When dealing with closed-off cuticles, you'll need products that can penetrate stubborn strands to deliver some much-needed moisture. Look for formulas containing lightweight ingredients, such as grapeseed and jojoba oils as well as glycerin, suggests Petrillo. ICYDK, glycerin is a humectant, which means it can draw moisture from the air to your hair.

Equally as important as scoring the right solutions? Properly (keyword!) applying your low-porosity hair products. "When it comes to low-porosity hair, you don't want to apply an excessive amount of products because it won't all absorb into the strands, and it may even leave behind residues," says Petrillo. That's why he recommends shampoos with anti-residue formulas (often labeled as "clarifying shampoos") and conditioners specifically marked as "lightweight." (But if you do end up with product buildup and residue, just treat your scalp to a detox.)

Low-Porosity Hair Products

Left: Amazon
Center: Ulta

How to Treat High-Porosity Hair

High-porosity hair characteristics include a tendency to tangle easily and susceptibility to high heat, heavy chemicals, and bleaches, says Petrillo. "You want to properly condition this hair type with formulas that lean more towards sealing in moisture." That means oils and butters are your friends. (See also: The Best Hair Oil for Your Hair Type)

"For porous hair strands, some of the best types of products are always going to be products that are formulated and marketed to add moisture and have a lot of emollient ingredients," says Williams. "Those include your butters and your oils, like olive oil, coconut oil, argan oil, castor oil, and shea butter. They really help to infuse moisture into the hair and seal in the moisture." For people with high-porosity hair, she also suggests deep conditioning each time you wash your hair.

Products with proteins are a common rec for high-porosity hair since they can strengthen dry, brittle strands. But you want to be careful to avoid going overboard. "Hydrolyzed proteins are good for the hair, but daily application can become too much and cause the hair to dry out," explains Williams. (Related: Try These DIY Hair Masks to Treat Dry, Brittle Strands

High-Porosity Hair Products

Center: Curlsmith
Right: Amazon

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