So you've done all the “porosity tests” and you still have no idea what your porosity is. You've floated hair in a cup of water, felt it for bumps, and sprayed water on it. You did not get a single consistent result from test to test.

Or you did get a consistent result and it told you your hair is “high porosity,” but all the recommended products weigh it down or behave nothing like you were promised.

That's because internet porosity is inconsistent and used to describe several unrelated things, many of them rooted in hair myths. Porosity advice is of limited use because of it.

By the end of this post you'll understand what can be salvaged from the internet's mess, and what to leave behind.

Much of this post is educational, but if you want to skip to the practical tips I suggest reading “TLDR” and then “Practical Takeaways”

If you get confused, check out our helpful glossary of terms used.

TLDR

People use “hair porosity” to mean two different things

• Damage porosity : Porosity reflects how compromised the hair fiber is. Undamaged hair is “Low porosity”. What’s called “high porosity” is damaged hair.

• Internet porosity : Here porosity is used as a catch-all for how hair interacts with water and products, treating low, medium, and high porosity as inherent traits even in healthy hair.

The problem is that internet porosity bundles together unrelated hair behaviors and blames them all on porosity, leading to contradictory tests and advice.

Damage porosity has limited practical value unless your hair is damaged. For hair care decisions, curl pattern, strand thickness, density, and product formulation matter far more.

The Two Porosities

Porosity as Hair Damage

Damage porosity refers to the physical condition of the hair fiber itself ^[20]:

• Low porosity hair has an intact cuticle and is undamaged.
• High porosity hair is damaged hair with a compromised cuticle. The compromised cuticle more readily lets products and water inside to the cortex (permeability).

You may have seen this definition used in many science books, podcasts, or videos ^[21][22].

Illustration of mixed porosity, showing how roots have less damage than ends

But many people have “mixed porosity”, which is multiple porosities at once ^[23]. Because damage accumulates over time, porosity varies along the length of the hair. Roots are lower porosity than ends, which have experienced more weathering from washing, styling, UV exposure, and general wear.

If hair is majority high porosity, it's a result of damage from stressors like chemical treatments or extreme heat. It may benefit from treatments (like protein or bond repair), products that reduce water swelling in the hair (for example, bond repair products with ingredients like citric acid), and cationic conditioners.

Damage is one of the few situations where porosity meaningfully changes what works on the hair.

In damaged hair, the lipid layer is stripped away, leaving a negatively charged, hydrophilic surface. Cationic conditioners are effective here because their positive charge allows them to bind to these damaged areas and form a protective coating.

Healthy hair has a fatty surface layer (F-layer). Oils adhere to this layer because like attracts like.

When the F-layer is lost, negatively charged groups are exposed and the surface becomes more water-loving. Oils are no longer attracted and may be repelled by water if hair is wet.

Positively charged (cationic) conditioners bind to the negatively charged surface, forming a protective coating that protects the hair and makes it look/feel better

High porosity can be a spectrum. There was one study I read where the scientists bought damaged “high porosity” hair but decided it wasn't damaged enough, so they damaged it more ^[24]. Reminds me of when I used to box dye my hair red and thought I knew damage. When I bleached it platinum blonde it was a whole new world of much worse damage.

Low porosity in this world represents the baseline state of structurally healthy hair. It's how your hair grows out of your head before it gets damaged by everyday stress or chemical treatments.

The damage definition is the definition of porosity currently used on CurlsBot's quiz.

Internet porosity

Internet porosity describes personal experiences with how hair interacts with water and products, rather than the physical condition of the hair fiber itself. It posits that porosity can vary in healthy hair. In internet porosity, whether healthy or damaged, hair can be low, normal, or high porosity.

In this model low is not a “normal” state, there is a separate porosity for that — “normal porosity ” or “medium porosity ”. This was the model that CurlsBot's quiz used originally, and is common on the internet.

In internet porosity, low porosity is not treated as a neutral baseline but as a special case that requires workarounds ^[25]:

• Can be dry because it supposedly ”resists moisture” getting inside the hair
• Prone to build-up from heavy or protein-rich products, which can lead to “overwashing“
• Needs to use heat and warm water to get moisture/products in

Whereas high porosity:

• Can be damaged OR intrinsic property of individual's hair
• Can feel“dry”
• Swells because it absorbs too much moisture, resulting in tangling, frizz, and breakage
• Needs to have moisture ”sealed in” with heavy products like oils and butters
• Should avoid humectants because they ”cause the hair to absorb too much water”

The top Google results for porosity mix damage porosity and internet porosity together. These sources describe high porosity hair as both damage AND an intrinsic property of hair ^[24] and prescribe the same treatment regardless of how the hair became high porosity.

As we'll learn later, damaged hair is biologically different than hair that while healthy, feels dry or absorbs water readily.

What Science Says About Porosity

Neither model explains how hair interacts with water, and current research does not yet support a single replacement framework.

For example, tightly curled/coily hair has been found to be higher porosity than straighter hair ^[2]...but it can also be MUCH more water resistant ^[14]! This sounds contradictory only if porosity is treated as a single property, which it isn’t. Recent science has found that water resistance in tightly curled/coily hair might be because of a unique hydrogen bond between strands of hair.

This brings us back to the damage model, which only recognizes high and low. This isn't consistent with the science that shows natural variation in porosity.

Evidence does exist for porosity variation in healthy hair, but it’s sparse and not yet actionable for everyday care. But in this research it has been found that ^[2][26]:

• Straighter hair tends to be lower porosity
• The curlier the hair the higher the porosity
• Permeability can be affected by genetic variations in lipid content and cuticle thickness
• Permeability may increase with age (but this is from one study)^[27]

It's going to be really hard to translate this to practical advice. I'm not sure it's enough for me to modify the CurlsBot porosity quiz.

My experience with porosity

I have frustrating hair because part of my hair is different from other parts.

• The part in the front is ash blonde naturally, repels water YET feels dry AND is easily weighed down/over-conditioned
• The other parts are dark brown; these areas don't react abnormally to water OR products, and consistently feel silky

I shaved my head once to see if the problems with the front part were damage but they weren't. I suspect they are a mix of “meandering hairs“ from aging ^[28] and the “irish curls“ pattern.

I'm pretty sure my hair is low damage porosity (it's short, I don't do chemical treatments). For internet porosity I can't tell my type because of all the mixed signals.

Personally for that dry feeling area I find advice for “rough“ hair much more useful than advice centered around porosity. The best treatment has turned out to be masks that soften but are not so heavy that my waves end up weighed down.

The Myths of Internet porosity

To write this I collected various advice about porosity from places like Tik-tok, blogs, and Pinterest.

Examples of internet porosity advice

The Tests

There are several popular “tests“ for porosity, and these are confusing because they all test for different things.

• Float test (floating a strand of hair in a glass of water, floats on top = low porosity, float in the middle = normal porosity, sinks to bottom = high porosity): Mostly reflects water resistance and surface conditions and is affected by products, buildup, length of the strand tested, and other factors that have nothing to do with either type of porosity^[29]
• Slide or bump test (feeling the surface of the hair for bumps, bumps = high porosity): This can detect high damage porosity by feeling for roughness in the cuticle, but can be inaccurate if people don't know how to distinguish hair damage from natural texture variation.
• Stretch test (stretching out the hair to see how it responds): Measures elasticity, which is influenced by many variables beyond porosity
• Spray test (spraying water on hair to see if it beads up on the surface which would mean low porosity or soaks in which would mean high porosity): Measures resistance to water which can be affected by curl pattern, products, and many other factors beyond cuticle porosity

Because each test probes a different property, disagreement between them is expected rather than diagnostic. There's nothing wrong with your hair if you get different results.

The Myths

Internet porosity is built on common hair myths that don't hold up to scientific scrutiny.

Moisture Myth

This is that more moisture = good and low porosity hair needs special treatment to get moisture inside. In reality for healthy hair, the moisture content inside is mainly affected by the humidity of the air around us ^[30]. You don't need to push anything inside of healthy hair, the water vapor is going in and out of its own accord.

This doesn’t mean hair can’t feel dry or rough, but that internal water content is not something products meaningfully increase in healthy hair.

There may be a benefit in tightly curled/coily hair types to using simple humectants (which attract and retain moisture) inside the hair. Luckily these are small molecules capable of penetrating through the gaps in healthy cuticles. How exactly they work is unknown, but there are a few studies that show they can reduce breakage in tightly curled/coily hair ^[31] .

Internet porosity advises people with high porosity hair to avoid humectants because they supposedly cause the cuticle to swell. This may prevent many people from using effective products that can prevent breakage.

Sealing Myth

Internet porosity says it's important to “seal” moisture into hair with emollients like oils. But no ingredients are known to form a true seal on the hair's surface. Instead they sit on the surface as blobs with gaps big enough to allow water vapor (which is quite tiny) to get in/out ^[30][31].

This goes along with the myth that porosity governs how much and how fast water vapor leaves or enters hair, which scientifically is a concept called permeability that is complicated and not useful for applying to haircare yet ^[26].

Research suggests that altering water content in hair is difficult. The ingredients that are promising are not“sealing” ingredients, but humectants that can attract and retain moisture, and ingredients that can potentially prevent too much water from hanging out inside the hair like citric acid ^[31].

Cuticle Opening myth

Cuticles DO NOT OPEN/CLOSE except for with chemical treatments with high pHs that damage the hair ^[32]. These changes involve cuticle disruption, not a reversible opening and closing mechanism.

If someone tells you that you need to open your cuticle up with heat or water or close it with cold water or vinegar, that's not what's happening.

The penetration myth

This is the idea that it's bad that products can't get inside low porosity hair. Accordingly special things need to be done to get them past the cuticle the hair shaft into places like the cortex. This goes along with the idea that it's bad if products are on the surface of the hair.

But the reality is that most haircare ingredients don't penetrate and aren't supposed to. Being on the surface isn't “bad”, products on the surface can be useful for making the hair look and feel good, and protective against damage.

Formulators/cosmetic chemists know that penetration inside the cortex is hard. The only hair products that usually rely on penetration to work are those formulated for damaged hair, but even though damaged hair's cuticle is impaired, it's a challenge to get ingredients inside ^[30].

The Advice

Now it's time to look at the advice I've seen on places like Pinterest or Tik-tok.

LCO for low porosity, LOC for high

LCO stands for liquid, cream, oil, and LOC stands for liquid, oil, cream. Same stuff, but different order.

LCO and LOC are known to be beneficial for tightly curled/coily hair types, but they will likely over-condition other types of hair.

Impact of LCO and LOC on hair breakage, LOC had lower breakage than LCO (which is good)

There is little science about LCO/LOC, but the one study that exists suggests you should pick LOC regardless of porosity for breakage prevention ^[33], but it was a small study that was never published in a peer-reviewed journal.

And as I noted before, oils are not as beneficial for hair that's damaged and cationic conditioners that stick to damaged areas are considered a better choice.

In the end, leave ins, creams, and oils are types of conditioners and the type and amount of conditioning you need depends on damage level, curl pattern type, strand width (fine or coarse), and other factors that are much easier to understand and measure than internet porosity

Verdict: LCO might be beneficial for tightly curled/coily hair types

Low porosity = you have to use heat to deep condition

There isn't much science on this, but I imagine it would benefit anyone who is doing oil/butter based deep conditioning. Masks and other deep conditioning treatments don't literally add moisture to the hair, but are instead full of emollients that can soften and smooth hair.

Deep conditioners are formulated to work for any type of hair using the instructions on the label. Unless the label says to use heat, you don't have to use heat for them to be effective.

There is one study that showed that using heat with a conditioning treatment improved how hair felt and looked, but unfortunately I can't read the study because it's in Korean ^[34].

Verdict: Deep conditioning with heat isn't essential for any type of hair

Clarifying is for low porosity hair

This might lead people with high porosity hair to avoid clarifying, even when they need it, which can lead to product buildup that just makes hair feel worse.

Verdict: If you have product buildup and your hair is damaged or fragile, look for a gentle clarifying shampoo or treatment. Examples are Bounce Curl's Gentle Clarifying or Aveeno Apple Cider Vinegar Blend Clarify & Shine Shampoo

Low porosity needs to apply products to wet hair

Whether to apply product to wet or towel-dried hair has nothing to do with porosity. It has to do with the particular product and preferences. Thankfully many manufacturers are providing more specific guidance for products. I appreciate that brands that have detailed instructions for their products.

Anecdotally I find wet hair application useful for products that can be hard to distribute like thicker creams. And towel-dried hair application useful for products I use to add texture (and are easy to distribute) like mousses.

I wish there were a standard rule for how to apply products to hair, but each product is different and it may depend on your curl type, strand width, and other factors that differ between people.

Verdict: Look for instructions from the manufacturer for how to apply products. If that doesn't work you can experiment with different water levels

High porosity needs protein treatments and low porosity should avoid protein

Protein treatments might benefit damaged hair, but they are not going to do anything to undamaged hair, except potentially over-condition it. I have a whole post on the myth that protein is bad for low porosity hair. There are thousands of types of proteins in haircare products with different roles and properties and saying to avoid ALL of them is like saying to avoid all vegetables because you're allergic to broccoli.

In the world of treatments for damaged hair, there are many other choices beyond protein treatments, like bond repair. A few bond repair treatments are protein-based, but many aren't.

Verdict: Don't avoid all protein because your hair is low porosity (either definition), and if your hair is damaged consider bond repair instead of protein treatments.

Heavy products are for high porosity, light products are for low porosity

In internet porosity, it's commonly believed that heavy products are best for high porosity and light products are best for low porosity.

Heavy and light don't always have consistent definitions, but the most common usage I see is:

• Heavy = rich in emollients like oils and butters
• Light = water-based formulations, rich in humectants

Oils and butters are emollient conditioners, which provide strand lubrication that protects from friction damage and tangles ^[25][35].

Humectants are conditioners that may affect water content in hair, as they attract and retain moisture ^[36]. They may be uniquely beneficial for tight curls/coils ^[31].

In the end both are conditioners, and framing it as if you need to choose one not only ignores the benefits of both, but means you're not considering the entire world of other conditioners like cationic conditioners, fatty alcohols, silicones etc.

Tightly curled/coily hair in particular might benefit from BOTH humectants and emollients (among other conditioners) ^[31][2].

Emollients like butters and oils can get a bad rep because using too much can lead to over-conditioning, a condition where your hair may feel soggy, greasy, and weighed-down. In loose curls/waves it can flatten the hair into a stringy mess ^[37].

Conditioning Trade-off Curve: As conditioning increases, volume decreases much more for wavy hair than curly hair

BUT the solution to that is NOT to never use emollients, but to find an amount and type that work for you. And also to explore emollients beyond just oils and butters, like silicones and fatty alcohols.

The traditional advice for high porosity ignores other factors such as curl pattern, damage level, and strand width. Oil/butter heavy products are not ideal for someone with fine hair for example, regardless of their porosity. And as I said before, cationic conditioners work better than oils/butters in damaged hair.

Verdict: Whether you need heavy or light products depends on factors other than porosity

The Products

I also looked at product lists for low and high porosity hair, and they were very inconsistent. Here are a few examples

Design Essentials, Almond & Avocado Curl Stretching Cream

• Seen recommended for: Low porosity hair
• Who it's actually for: Tightly curled/coiled hair if you want elongation
• Who it's terrible for: Loose curls/waves, it's too heavy

k18 Peptide Prep

• Seen recommended for: Low porosity hair
• Who it's actually for: K18 products are formulated for damaged hair (from chemical processing or heat).
• Who it's terrible for: No one, though it's kind of a waste of money for undamaged hair

Grapeseed oil or avocado oil

• Seen recommended for: Low porosity hair
• Who it's actually for: Anyone, though these tend to be lighter so they are more likely to work decently for finer hair than thicker, heavier oils like coconut/castor oil or butters like shea butter
• Who it's terrible for: Beginners who are not used to using plain oils on their hair and end up using too much, over-conditioning their hair. They are better served by a serum of some kind that is a blend of oils and other ingredients.

Shea Moisture Intensive Hydration

• Seen recommended for: Both high and low porosity hair depending on the list
• Who it's actually for: This product is probably great for dense medium/large strand tightly curled/coily hair.
• Who it's terrible for: Anyone with easily over-conditioned hair such as fine hair or loose curls/waves

Apoghee Two-step Protein Treatment

• Seen recommended for: High porosity
• Who it's actually for: This is for hair that's been damaged by chemical processing
• Who it's terrible for: Both a waste of money for undamaged hair and could lead to over-conditioning

The Verdict: Who these products work for has nothing to do with porosity (except the ones for damaged hair) and everything to do with other factors like strand width and curl type.

Practical Takeaways

If your hair is significantly damaged

Damage-based porosity can be useful here. Hair that is heavily bleached, chemically treated, or heat damaged tends to be more permeable and structurally compromised.

This is where damage-focused strategies can help, such as

• treatments designed to reinforce or repair the hair fiber like bond repair
• conditioners that bind well to damaged surfaces (cationic conditioners), typically found in conditioners that are labeled for damaged/treated hair
• approaches that reduce excessive swelling from repeated wetting like some acid-based bond repair treatments ^[38]

In this context, what’s often called “high porosity” is a meaningful signal that damage needs to be addressed.

If your hair is high porosity in the damaged sense, and also easily weighed down -- I’ve put together a more detailed product guide in an ebook:

Get our free lightweight products guide! It has tips for finding light products at any store with dozens of example products and routines

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If your hair is mostly undamaged

Porosity is unlikely to be a helpful organizing principle.

Healthy hair maintains an internal water content based almost entirely on the water vapor in the air. You do not need to force water into it or avoid ingredients based on porosity labels.

If products feel heavy, ineffective, or unpredictable, the cause is better explained by

• curl pattern and geometry ^[37]
• strand thickness and density
• how concentrated or film-forming a product is
• how and when it is applied

Undamaged also doesn't mean impervious to damage. It's important to protect undamaged hair from everyday stressors like UV and friction. That's why I personally started using a light leave-in with UV protection. If you use heat, you'll want to use a heat protectant.

What porosity does not reliably tell you

Porosity alone does not determine

• whether your hair needs oils, butters, or humectants
• whether protein-containing products will help or hurt
• whether products should be applied to soaking wet or towel-dried hair
• how your hair will behave in different weather

For example high porosity hair in the damaged sense might do best with light products (in terms of conditioning, especially emollience), if it's fine, loose curls/waves, or thin.

What to focus on instead

For most people, better results come from paying attention to properties that consistently matter

• curl pattern and degree of curl tightness
• strand thickness and overall density
• level and type of damage along the hair length
• product formulation and application method
• environmental factors like humidity
• scalp condition and how it affects cleansing frequency and product tolerance

Porosity is not meaningless, but it is a minor variable compared to these factors.

Conclusion

Hair porosity became confusing because it was asked to explain too many different things. Real differences in hair structure, curl geometry, surface chemistry, and damage were all folded into a single label and treated as if they shared one cause.

When porosity is used narrowly to describe structural damage, it has a specific value. It can help identify hair that is compromised and likely to benefit from damage-focused care. Outside of that context, porosity quickly stops being a useful organizing principle.

The behaviors people attribute to porosity are better explained by factors that are easier to observe and more consistent over time, such as curl pattern, strand thickness, and density.

If there is a takeaway here, it’s that you don’t need to diagnose your porosity to take good care of your hair. Understanding what porosity can and cannot explain is more helpful than trying to assign yourself a porosity type.

If you want to assess damage-related porosity, the CurlsBot porosity quiz can be a useful starting point. If you’re interested in curl pattern, there is also a separate hair type quiz.

Glossary

Porosity is the damage level of the hair. Take our porosity quiz to find yours

Thin

Thick

Density describes how many hair strands you have per square centimeter

Fine

Coarse

Strand width refers to how thick each individual strand is, often called "fine" or "coarse"

• Cationic conditioners: ingredients that are positively charged, which allows them to stick to negatively charged surfaces easier
• Chemical processing: Any hair treatment that involves chemical reactions that change the hair such as bleaching, most dyes, highlighting, perming, and relaxing
• Conditioner: an ingredient that protects, softens, smoothes, or otherwise improves the condition of hair
• Density: The number of hair follicles per area, with a low number = thin, and high number = thick
• Emollient: Conditioning ingredients that reduce friction to protect the hair like oils, butters, silicones, and fatty alcohols
• Heavy: usually used to describe products that are dense and high in fat-based emollients like oils or butters
• Light: usually used to describe products that are less dense (like liquids/foams) and low in fat-based emollients like oils or butters
• Loose curls/waves: Hair with high elongation and low shrinkage, AKA types 2a, 2b, 2c, or 3a in conventional typing
• Over-conditioning: When too much conditioner is used on hair. Can make it mushy and greasy or brittle and frizzy depending on the type of conditioner.
• Permeability: the speed at which substances like water vapor enter and exit hair
• Porosity (damage): how intact the cuticle is, which affects permeability
• Tight curls/coils: Hair with high shrinkage, AKA types 3b, 3c, 4a, 4b, 4c in conventional hair typing or “Afro-type“ hair in some literature
• Shrinkage: The difference in length between hair in its dry resting state and stretched out
• Strand width: The thickness of individual hair strands, small = “fine”, large = “coarse”

About the Author

Melissa McEwen is the creator of CurlsBot. She is a software developer with training in science writing and a B.S. in Agricultural Science. Her writing has appeared in publications such as NPR and Quartz.