We earn a commission when you buy through the Amazon links on this page. How this works.
Hair is made almost entirely of a protein called keratin. Water gives it flexibility. A healthy curl has enough of both: strong enough to hold its shape, supple enough to stretch and spring back. When curls misbehave for no obvious reason, the cause is often that one has outrun the other.
What each one does
Protein is structure. The hydrolyzed proteins in hair products, which appear on labels as hydrolyzed keratin, wheat, silk or rice protein, or as amino acids, are small enough to cling to damaged areas of the cuticle and patch them for a while. Hair feels stronger and curls hold their shape better. The effect washes out over time.
Moisture is flexibility. Conditioners, humectants such as glycerin, and the oils and butters that slow water loss keep the strand soft and elastic.
Signs you need protein
- Curls that are limp, stretched out and will not hold a shape.
- Hair that feels overly soft, mushy or gummy when wet.
- Strands that stretch a long way and do not spring back.
- Recent bleach, color or heat damage.
Signs you need moisture
- Hair that feels rough, stiff or straw-like.
- Strands that snap with very little stretch.
- Dullness and persistent frizz.
- A routine that is heavy on strengthening or repairing products.
The stretch test
Take a single wet strand and pull it gently between your fingers.
| What happens | What it suggests |
|---|---|
| Stretches a little, returns to length | Balanced |
| Stretches and stretches, stays long or breaks | More protein |
| Barely stretches before snapping | More moisture |
It is a rough guide, not a laboratory result. Repeat it with strands from a few places, and trust a pattern over a single hair.
Too much protein and too little moisture look almost identical. Check your shelf before you buy a cure.
If you need protein
Start gently. A conditioner or mask with protein in the first half of the ingredient list is enough for most hair.
For hair that has been badly damaged by bleach or relaxers, there is a stronger option.
If you need moisture
Set the protein products aside for a few weeks and deep condition with something protein-free, weekly. Look at your stylers too: many gels and leave-ins contain protein, and the total across a routine adds up.
Where bond builders fit
Products such as Olaplex are often filed under protein. They work differently, targeting the internal bonds that bleach and heat break, and they contain no protein in the usual sense. They are most useful on chemically treated hair.
A word on porosity
High porosity hair generally welcomes protein, because it has gaps to fill. Low porosity hair often needs very little. If you do not know which you have, read Hair Porosity, Explained first.
Keeping the balance
Most curls do well with a moisturizing deep conditioner most weeks and a protein treatment every four to six weeks. Adjust from there. The aim is not a fixed schedule. It is to notice how your hair feels wet, and respond.