What is hair porosity?

Developing the right routine for your specific hair needs is no easy feat. Much like with skincare, there is scientific reasoning behind the way your curls, coils, and waves respond to certain products and styling methods—even the rate at which they absorb and retain moisture, otherwise known as hair porosity. If waiting hours for a protective style to fully dry or having to re-wet sections of your hair mid-blowout sounds familiar, both situations can be a telltale sign about its porosity level.

A strand of hair contains three layers: the cuticle, cortex, and medulla. The design of the cuticle layer, in particular, is similar to that of window blinds: When the blinds are open, sunlight can flow in; when they're closed, light is blocked. Your hair cuticles are also able to open and close, but instead of light, they receive hydration and nourishing ingredients used in your routine. The porosity level of your hair ultimately determines how seamlessly cuticles allow moisture in and out of the hair shaft.

Proper nourishment is a nonnegotiable for stronger, more fortified hair, which is why determining your porosity level—low, medium, or high—is key. Once you know which essentials actually work best for your specific needs, it is simple to upgrade your entire hair care routine. For more tips on determining your unique level and product suggestions for each, we asked professionals about everything you need to know about hair porosity.

What is hair porosity?

Hair porosity—how porous your hair is—refers to your hair’s ability to absorb and retain moisture, and is not specific to its texture. “All individuals of any ethnicity and hair type have a porosity level and some even have a mixture of porosity,” hairstylist Deanna Brown, known as the Curl Doula, tells Bazaar. Ultimately, porosity determines the types of products that are most beneficial to hair’s overall health, along with the essentials most effective for achieving a desired look.

What are the most common types of hair porosity?

There are three basic levels of hair porosity: low, medium, and high.

Low-porosity hair typically doesn’t allow moisture in or out of the shaft easily, due to tightly packed openings in the cuticle. This porosity level also indicates that hair cuticles take longer to absorb and repel water than others. Brown notes that this level often gets a bad reputation for attracting build-up, as it takes low-porosity types a little extra elbow grease to achieve a thorough cleanse.

Medium to “normal” porosity is especially ideal in hair, as these types of cuticles tend to be a Goldilocks fit between tight and loose, seamlessly allowing moisture to enter and exit. Since this porosity type accepts and retains moisture easily without quickly losing it, the maintenance process includes less guesswork overall.

High-porosity hair quickly absorbs moisture but loses it just as fast, thanks to its loose cuticle structure; they open easily and do not close as tightly as cuticles with lower porosity levels. According to Brown, when this type is unmanaged, hair can become extremely dehydrated, as well as prone to breakage and tangles. As a result of excessive styling and heat, celebrity hairstylist Kelly Novobielski says, many people unknowingly have high-porosity hair, which can be identified by dry or damaged ends.

While all hair has a natural porosity, your level can change based the ways in which it is treated. “You can change the hair porosity for the worse by using excessive heat and styling without proper products,” Novobielski says. “This overuse will damage the hair’s cuticle, resulting in high porosity. You can combat this by using products regularly to moisturise and replenish the hair protecting it from heat and environmental damage.”

How can I determine my hair’s porosity level?

There are several methods you can use at home to determine your hair’s porosity. For one, Novobielski suggests testing the old tried-and-true “glass of water” trick: “You can put a strand of hair in a glass of water. If it sinks quickly, it probably has high porosity. If it floats or takes longer to sink, it has medium to low porosity.”

Brown agrees, adding that the test is best conducted on clean, product-free strands of hair. “Products will give you false results. Naked hair will be in its most authentic form, so you can truly see where your hair’s health is,” she notes. Brown also recommends testing different strands from a number of sections of your hair. “If you notice your hair is more hydrated in the nape versus the crown, it’s best to double-check, as your porosity can vary in different areas.”

What are the best hair care methods for each porosity type?

In the same ways porosity can be altered based on hair habits and chosen product rotation, it can also shift with the addition of suitable treatments and products. To help you get a head start on an effective routine, Brown and Novobielski weigh in ahead with some helpful tips and suggestions for each porosity level.

A Low-Porosity Routine

For low-porosity hair, Brown recommends starting with a gentle shampoo that doesn’t contain harsh surfactants. “Anything harsh will raise the cuticle and cause more problems for your low-porosity hair,” she says. Look for ingredients that will give hair great slip when styling, so that the hair doesn’t break easily. The expert also explains that it’s helpful to keep an eye out for ingredients that cleanse and hydrate the hair simultaneously. And once clean, make sure to sop up as much excess moisture as possible with a friction-free hair towel to help styling products absorb more effectively into your cuticles.

A Medium to “Normal” Porosity Routine

As previously mentioned, a long-standing goal for healthy hair is to achieve a medium or “normal” hair porosity level in each area of your scalp. Using a gentle, hydrating shampoo to remove product buildup, incorporating regular deep conditioning treatments into your routine, and protecting hair as you sleep with a silk or satin bonnet are key steps in helping to maintain this level of porosity. Brown also advises to avoid aggressive brushing, so a thorough yet gentle detangling brush is a great addition to your hair care routine.

A High-Porosity Routine

To replenish moisture loss and repair the damage often present in high-porosity types, professionals say using a richly hydrating leave-in treatment each day is a must. “A favourite of mine is the Better Natured Hydrating Leave-in Milk Treatment, Novobielski says. “It is perfect for those with high porosity as it revives dry and brittle hair, leaving the hair feeling nourished and soft.”

Brown stresses the importance of avoiding humectants like aloe vera, honey, and panthenol if you have highly porous hair. “Humectants are formulated to lift the cuticle, and in high porosity hair the cuticle is already lifted. If cuticles are lifted too high, they will not hold moisture,” she says.

Incorporate more emollient ingredients like hair oils, butters, and fatty alcohols, which are better suited for this porosity level for longer lasting softness and hydration. Deep conditioning your hair as often as possible can also help mitigate potential or additional breakage. Plus, prioritising healthy hair habits before bed can be game-changing for high-porosity levels. Experts suggest sleeping with a silk or satin pillowcase at night to guard against cuticles opening as a result of excess friction as you sleep, which later releases moisture.

Meet the experts

Deanna Brown is a professional stylist in Hollywood, Florida.

Kelly Novobielski is a celebrity hairstylist in New York City.

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All images: Unsplash, Pexels 

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