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Having dull and broken hair can be incredibly frustrating.

Thankfully, one tried and true treatment that you could trust is protein filler.

Woman applying serum to her damaged hair

Keratin, a key in of protein, is the primary structural element of a hair strand.

When these proteins undergo chemical or thermal damage, protein filler can help them repair their structure.

However, this is only true depending on what kind of state your hair is originally in.

Woman using shampoo brush

When the cuticle has flowered open, it creates opportunities for damage."

And, when this cuticle is opened up, the hair loses its ability to retain moisture.

In addition, the protein treatment also increased the strength of previously bleached hair by almost 200%.

Woman looking at hair in mirror

A reliable way to tell if your locks could use some protein filler is to evaluate their resiliency.

NYC-based hairstylist Matt Newman shared an easy way to test this elasticity withMind Body Green.

If it tears in half, you might need some protein filler.

Thus, if it doesn’t snap and passes the test, you should avoid protein treatments.

When your hair already has a sufficient supply, too much protein could lead to damage.