Signs You Have High-Porosity Hair — and How to Care for It

A trichologist shares how to tailor your hair-care routine if you suspect you have high-porosity hair.

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Hair Health Hotline is your direct access to dermatologists, trichologists, hairstylists, and other beauty pros. Each story in this series tackles a common hair or scalp concern and offers science-backed solutions to care for your strands.

A lot of factors impact the way your hair looks and behaves, from the rate that your scalp produces oil to your hair's curl pattern (or lack thereof). Another key characteristic? Your hair's porosity.

While you may associate the word "porosity" with sponges or kitchen countertops, your hair can also be classified by how easily water passes through it. If you have high-porosity hair, that means your hair soaks up — and loses — moisture relatively easily. Here, trichologist Angela Onuoha details how to confirm you have high-porosity hair, and if so, how to care for your strands accordingly.

Q: I've been getting my hair colored for years and now I have high-porosity hair. How do you fix high-porosity hair so that it no longer looks dry and damaged?

A: The most effective way to avoid the negative effects of high porosity is to limit damaging styling practices, according to Onuoha. That said, hair treatments can also offer temporary improvement, she says. But before diving into how to alter your routine, it's helpful to understand the differences between low- vs. high-porosity hair.

What Is High-Porosity Hair?

As mentioned, water more easily passes through high-porosity hair compared to hair that's on the low-porosity end of the spectrum. Your hair's porosity is a reflection of the state of the hair's cuticle, aka the outermost layer of each strand, explains Onuoha.

"You can view the outer layer as tiles that are piled upon each other just like a roof," says Onuoha. "Whenever damage occurs, and this can be in multiple ways, [the cuticle] will start to lift and as a result, the hair becomes more fragile since it's not closed anymore." High-porosity hair typically has a compromised cuticle layer that allows moisture to easily pass through. "High porosity, nine out of 10 times, is due to damage," says Onuoha.

Multiple culprits can lead to damage, including chemical treatments, styling with hot tools, and exposure to the sun's UV rays, says Onuoha. "It could be friction from your pillowcase," she adds. "It could be friction due to brushing or tension due to tight hairstyles."

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Photo by Juliane Falk.

What Are Signs of High-Porosity Hair?

While some pros suggest trying the "float test," — placing a strand of hair in a glass of water and paying attention to how long it takes to sink to the bottom — to figure out your hair's porosity, Onuoha doesn't recommend it. Too many other variables, from hardness of your water to the amount of product on the strand of hair, could impact how long it takes for your hair to sink, she says. "The only test that I would recommend is there's a lab that you can send your hair to that literally tests your strands," she says.

Worth noting, very few people have low-porosity hair, according to Onuoha. "As soon as your hair grows out and it is exposed to all these normal elements, you will have some type of rise in porosity," she says. "The average human being has medium porosity, which is totally fine." As a general rule, your ends will be more porous than the roots of your hair, since they've been exposed to damaging elements for longer, says Onuoha.

There are certain giveaways that your hair has incurred enough damage to reach the high-porosity end of the spectrum. For one thing, it won't reflect light and will look dull instead of shiny, says Onuoha. While a closed cuticle creates a flat surface that reflects light, a damaged strand of hair can look closer to a frayed rope up close, she says.

The best indicator of high-porosity hair is that your hair is noticeably more fragile than it used to be, says Onuoha. "Clients have shown me pictures saying, 'Back in the day, my hair used to be so much more shiny, I had much more defined curls or my ends were way fuller than they are now.' Those are all indications of more damage or high-porosity hair."

How to Choose the Best High-Porosity Hair Products

You can take steps to prevent your hair from becoming highly porous, but it's impossible to return strands to a lower-porosity state once the damage has been done, says Onuoha. Limiting your use of chemical treatments and heat styling and using hair products with UV filters are all preventative steps.

Additionally, it's helpful to use a microfiber towel rather than a cotton option when drying your hair, and to avoid frequent hair brushing, since both can limit friction, says Onuoha. "Over-brushing is a very easy way to cause damage to the cuticle and that will result into high porosity hair," she says. If you have straight hair, use a detangler and only brush your hair before each shower, and if you have textured hair, detangle your hair in the shower while your hair still has a conditioner in it, she suggests.

While prevention will have biggest impact, you can take steps to improve the appearance of high-porosity hair, says Onuoha. Leave-in conditioners can help smooth out your hair's cuticle, and bond-building treatments temporarily repair damage, she notes.

The more you like to have fun with styling your hair and changing its color, the more likely you'll end up with high-porosity strands. If you're disappointed that your hair is looking drier and more dull lately, you may want to look for ways to cut back on damaging styling practices and add treatments to your routine.

Have a hair health question you want answered? Send your Q to hairhotline@shape.com for a chance to have it featured in a future installment of Hair Health Hotline.

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