We Ask a Derm: What Is Porosity, and What Does It Mean for Your Hair?

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While we’re all relatively familiar with hair types, there’s an even bigger spectrum to consider within each group, and learning it is the best way to determine what kind of products work best with your strands. Whether you’re looking for a cream, butter or oil, figuring out your porosity is a great starting point to guide you toward better haircare.

What is porosity, exactly?

Basically, porosity is how well your hair absorbs and holds moisture. The type of porosity you have is determined by how easy it is for water or any other substances (aka oil, dirt or chemicals) to navigate through the outermost layer of the hair shaft, known as the cuticle.

“The hair cuticle plays a role in the porosity of the hair because it acts as a protective barrier to the hair shaft. The cuticle can be damaged by heat, over-manipulaton, or chemicals. Damage to the cuticle can thus alter the hair’s porosity.” said Dr. Karen Kagha, dermatology physician in Southern California.

There are levels of porosity: High, medium and low. While medium porosity is ideal because it holds the healthiest amount of moisture, none of them are necessarily bad, and using products specifically designed for your porosity level will leave your hair looking it’s best.

McKenzie Cordell

Ok, So How Do I Figure Out My Hair Porosity?

You don’t need to concoct a science experiment or head to your nearest salon to figure out your hair porosity. Here are three simple tests you can try right at home.

1. The Float Test

The float test is by far the most popular test of the three. All you’ll need is a strand of your hair (make sure the sample is clean and dry), a glass of water and...well, patience. Just grab some strands from your brush or pull a couple straight from your head (avoiding any strands around your face or go-to part line), drop a single strand into the glass of water and wait about 2 to 4 minutes for the results.

If the strand floats, that means you have low porosity. But if it sinks, your porosity is high. However, if your strand happens to be in the middle of the water, chances are you have medium to normal porosity.

2. The Slip ‘n’ Slide Test

No tools are needed for this one. Just grab a strand of hair and slide your fingers up towards your scalp. If you feel little bumps along the way, you have high porosity. (The ridges mean your cuticle is lifted and open.) But if it feels dense and brittle, you have low porosity. For medium porosity, the strand will feel smooth and glide easily on your fingers.

3. The Water Spray Test

This test is great for curly gals. Just spritz some water onto your curls and look closely before asking yourself, does it absorb quickly or do water droplets remain on the surface? If it soaked up all the water, you have high porosity. If it takes a moment to sink into your curls, you have low porosity. But if the water soaks easily into your hair and leaves a damp look, you have medium porosity.

Hopefully you’ve been able to pinpoint your porosity using the above tests, but if you’re still unsure, here’s a breakdown of each one and what it means for your hair.

1 low porosity
McKenzie Cordell

What Is Low Porosity?

Low porosity means cuticles are tight and overlapping. Hair has a tough time holding onto moisture (even if you try wetting it) while also resisting any kinds of chemicals penetrating through. OK, but is it bad to have low porosity? Not at all. Your hair just takes a minute to absorb water. It’s a bit shy when it meets moisture and needs a little push in the right direction.

Tips for you: Avoid any heavy butters, creams or oils since it will most likely weigh down your hair and lead to major product buildup. Instead look for clarifying shampoos and protein-free conditioners that won’t leave your hair feeling stiff and brittle or cause any excess build up. Dr. Kagha recommends checking out products with super penetrating humectant and emollient ingredients (aka glycerin and honey) to hydrate your hair.

When it comes to conditioning your hair, try using a steam, low heat cap or hooded dryer to get the job done. Since the cuticles are usually tight, more humid heat can help open them up and let some moisture pass through.

Shop low porosity products: Carol’s Daughter Almond Milk Restoring Conditioner ($11); Shea Moisture Curl Enhancing Smoothie ($13); Jessicurl Deep Conditioning Treatment ($15); tgin Moisture Rich Sulfate-Free Shampoo ($15); Giovanni 50/50 Balanced Hair Moisturizer Conditioner ($20); Mizani Miracle Milk Leave-In Conditioner ($34)

2 medium porosity
McKenzie Cordell

What Is Medium Porosity?

Medium porosity means cuticles are a just tad looser—the ideal porosity. Just the right amount of moisture goes in and out without any problems. Want to try a hairstyle? Go for it. Ready to color your hair? Do it. (Though it might alter your porosity over time.) You can forget having to deal with much maintenance when it comes to medium porosity since it's considered the “normal” of the three.

Tips for you: Try deep conditioning and protein treatments to maintain the balance of your moisture and hold. Dr. Kagha also recommends using liquid-based conditioners such as milks and creams, as well as butters and oils.

Shop the medium porosity products: Aphogee ProVitamin Leave-In Conditioner ($5); Shea Moisture Coconut & Hibiscus Curl & Style Milk ($9); Carol’s Daughter Sacred Tiare Restoring Hair Mask ($14); As I Am Hydration Elation Intensive Conditioner ($15); MoroccanOil Curl Defining Cream ($14); Innersense Hydrating Hairbath ($28)

3 high porosity
McKenzie Cordell

What Is High Porosity?

High porosity means cuticles are loose to the point that your hair may have some tiny gaps and holes in it. Hair has too much moisture (and also loses moisture easily) which can lead to frizz, tangles, dryness and breakage. Ouch, so it’s bad to have high porosity? Not at all. It doesn’t necessarily mean you have damaged and unhealthy hair. Your hair could just be more delicate, fine and in need of extra TLC.

Tips for you: Avoid glycerin and other humectant-focused products at all costs. Also avoid any silicones as they’re difficult to wash out and may cause buildup, leaving hair looking and feeling dry. Dr. Kagha suggests leave-in conditioners, moisturizers, butters (like raw shea butter) and oils (black castor, coconut or olive oil) to seal any damaged cuticles and prevent excess moisture from seeping through. Don’t forget to also use heat protectant products before using any heat tools.

Shop the high porosity products: Creme of Nature Moisture Recovery Leave-In Curl Milk ($5); As I Am Coconut CoWash Cleansing Conditioner ($8); Tropic Isle Living Jamaican Black Castor ($14); Shea Moisture High Porosity Moisture Seal Shampoo ($22); Ouidad Advanced Climate Control Heat and Humidity Gel ($26); Living Proof Restore Shampoo ($26)

But what causes porosity, and can it change?

It’s important to note that your porosity level is initially based on genetics, but that doesn’t mean it can’t change over time due to external factors. Cuticles can fuse together, open up or become damaged based on chemical processes (like perms, relaxers and color dye), heat tools or environmental exposures. Even excessive friction from scarves, hats and scrunchies can shift the outer layer’s relationship with moisture.

So be conscious of how your treat your hair and get to know it a little better. The more you give your locks what they need, the more you’ll find that they cooperate. Good hair days can be everyday.

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Associate Editor, Ultimate Fangirl, Aspiring Beauty Guru

Chelsea Candelario is an Associate Editor at PureWow. She has been covering beauty, culture, fashion and entertainment for over a decade. You'll find her searching the internet...