There may be more at play with your damaged hair than the obvious: achieving healthy hair runs deeper than simply choosing the right ingredients, styling tools, and products to keep your strands hydrated. While texture and density are key qualities in determining a proper routine for your hair, porosity could be the other major key missing from the equation.

If you didn’t realize already, moisture plays a critical role in overall hair health. For context, low porosity hair can retain moisture for considerably long periods (hence why your hair may take forever to dry, with or without a blow dryer. But the caveat? Its extremely flat cuticle layer also makes low porosity hair less likely to absorb water and nourishing hair treatments.

Low porosity hair can honestly feel like a double-edged sword to deal with, but there’s good news—we know just who to ask about maximizing its potential. For the ins and outs of caring for low porosity hair, we turned to top dermatologist Joyce Park, MD, as well as curl specialists Marissa Rullan of Studio 210 and Leigh Hardges from Maxine Salon. Below, learn everything from how to find out your hair’s porosity to what to look for on product labels.

Keep reading for their tips on how to care for low-porosity hair on wash day and beyond.

What Is Hair Porosity?

Hair porosity refers to how your hair retains and absorbs moisture based on how open or closed the cuticle layer (the outermost layer) is. To better understand the role of the cuticle in hair porosity, here’s what you need to know about the structure of hair strands: “The medulla is the innermost layer of the hair shaft, and it is composed of cells and air spaces and is generally more prominent in thick or coarse hair,” Park says, “The cortex is the middle layer and makes up the majority of the hair structure. It contains keratin, which provides strength and elasticity to the hair. The cortex also determines the color and texture of the hair.”

“Then we have the outermost layer of the hair shaft, the cuticle, which consists of overlapping, transparent cells that resemble shingles on a roof,” Park continues, “The cuticle serves as a protective layer for the cortex, preventing damage and contributing to the hair’s overall strength and shine. The health and condition of the cuticle also affects the hair’s texture and appearance.”

What Is Low Porosity Hair?

Low porosity hair has a tightly sealed cuticle layer, making it resistant to moisture absorption. “Such hair often feels smooth and can seem resistant to styling products,” says Park.

“Low porosity [hair] is typically caused by genetics, while high porosity can result from environmental damage, excessive heat styling, or chemical treatments,” she adds.

How to Determine Your Hair’s Porosity

Curious how to test your own hair’s absorbency abilities? Park and Rullan say there are two at-home ways to do so: the sink or float test and the spray bottle test. “These tests provide insights into your hair’s ability to absorb and retain moisture, helping you tailor your hair care routine accordingly,” Park says, “[But] keep in mind that individual hair strands may vary, so it’s helpful to consider the overall pattern across your hair.”

Try the Sink or Float Test

For the sink or float test, “You’ll take a few strands of hair that have naturally shed from the scalp and fill a cup with room temperature water,” Rullan explains. “Remember, hot water opens the cuticle, so if the water is too hot, regardless of the porosity, the hair will load up with water and sink. High porosity is so open; the hair will quickly absorb water and then sink to the bottom of the cup. Low porosity hair is water-resistant, which means the strands will remain floating towards the surface even after a few minutes. If the hair hovers in the middle, you have medium or (normal) porosity which absorbs and retains water well.” 

Test with a Spray Bottle

Next is the spray bottle test. “You’ll simply mist a section of the hair and closely watch,” instructs Rullan. “If the water beads up and fails to absorb, maybe even rolling off of the hair after a few minutes, you have low porosity hair.”

How to Take Care of Low Porosity Hair

“Understanding your hair’s porosity helps tailor a hair care routine,” according to Park. Here are the best tips on how to take care of low porosity hair, according to the experts:

Moisturize Using Emollient Ingredients

“High-porosity hair frizzes out when exposed to humidity and becomes more easily dry and brittle in dry heat,” says Rullan. “Low porosity hair is moisture resistant because the cuticle layer is so tightly closed that water molecules are too big to penetrate the hair shaft.” In other words, moisture is the key no matter your hair’s porosity; look for products with emollients—or softening ingredients such as aloe, avocado, jojoba oil, and shea butter—as they form a barrier and trap water.

Embrace Warmth

“Caring for low-porosity hair involves utilizing heat, such as warm water and heat-based treatments, to enhance product absorption,” Park says. Why? Warmth has the ability to open hair’s cuticles, allowing for nourishing products to penetrate deep into strands. If you plan on using hot styling tools on your low porosity hair, Park recommends the Kérastase Nutritive Heat Protecting Leave-In Spray “because it offers both heat protection, while it also deeply moisturizes.”

Wash Hair Using a Sulfate-Free Shampoo

Rullan also recommends all hair types always use a sulfate-free shampoo, as sulfates can be quite drying. For those of us with drier hair, she recommends pairing your shampoo days with your mask or treatment day because, as she puts it, “No matter the porosity, the essential goal with styling is to aid in water retention creating a shiny, juicy curl.” And if you’re working with tangled hair, Hardges recommends that you “be gentle when you’re detangling the hair while wet. Remove tangles starting at the ends and work your way up.”

Lock in Moisture with a Deep Conditioner

As for styling, Rullan says moisture-locking products are best. “We want to trap in as much water as possible. Squeeze out excess moisture before applying product, but don’t towel dry. With low porosity hair, steam from the shower is helpful, so use that to your advantage.” Hardges recommends using a deep conditioner in lieu of a regular conditioner as they “are thicker and more concentrated.” For an extra dose of shine, “Use apple cider vinegar after rinsing out the mask to help close the cuticle. This strengthens the strands and makes for a shinier finish,” says Hardges.

Add Protein Treatments to Your Routine

Protein treatments can help reinforce and repair the hair’s structure, minimizing breakage and promoting strength, according to Park. This is especially beneficial for low-porosity hair, which can be more prone to damage due to limited moisture intake, making strands brittle.

Maintain Hydration with Protective Styles

Rullan left us with a few gems at the end of our chat: “If definition and moisture retention are your priority, twists, braid-outs, and Bantu knots are the way to go. These sets help trap moisture in and allow more time for the hair to slowly but surely absorb moisture.”

Lastly, she adds, “Sometimes, when people decide to embrace their natural texture, they assume it will be easier. Although natural is healthier, it’s not necessarily easier—in fact, for some, it may imply more work. Rest assured, the work is worth it for happier, healthier hair. You get out of it what you put into it.”