Hair Porosity 101: Why the Same Product Works for Your Friend but Not for You
You buy the serum your friend swears by. You use it the same way. And your hair ends up weighed down while theirs looks effortless.
The product didn't change. What changed is porosity: how easily your hair's outer layer lets moisture in, and lets it back out.
What porosity actually is
Your hair's outermost layer, the cuticle, is made of tiny overlapping scales. How tightly or loosely they sit decides how easily water, oils, and product ingredients get into the strand, and how easily moisture escapes afterward.
The three types
Low porosity: The cuticle sits tight and flat. Hair takes a while to get wet, and products tend to sit on top and build up. It holds on to moisture well once it gets it.
Medium porosity: The easiest type to manage. Moisture goes in at a steady pace and stays. It usually responds well to most products.
High porosity: The cuticle sits open, either naturally or because of heat styling, colour, sun, or chemical treatments. Hair absorbs moisture quickly but loses it just as fast, so it often feels dry and frizzy.
Two quick tests
- The float test: Drop a clean, dry strand into a glass of room temperature water and wait about five minutes. Floating points to low porosity. Hovering in the middle points to medium. Sinking quickly points to high.
- The touch test: Run a clean, dry strand between your fingers. Smooth suggests low porosity. Rough or bumpy suggests high porosity.
Matching your routine
- Low porosity: Lightweight, water-based products. Apply to damp hair, and clarify occasionally to prevent buildup. Gentle heat helps a deep conditioner absorb.
- Medium porosity: Standard products work well. The goal is to avoid heavy heat and processing that can push hair toward high porosity.
- High porosity: Richer creams, oils, and leave-ins to seal moisture, plus protein-based masks to rebuild structure. Cut back on heat and chemical treatments while it recovers.
Once you know your porosity, choosing products stops being guesswork based on what worked for someone else.
For a more detailed guide to the science and testing methods: https://www.emedihealth.com/skin-beauty/hair-scalp/know-your-hair-porosity
And to find formulas suited to how your hair actually absorbs moisture, browse our range: https://www.cosmosentials.com/
Do you know your hair's porosity type? Tell us in the comments.
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