Recently I've learned that, though hair does need protein, there is a such thing as too much protein and too much can cause more damage than good. The benefit of protein is to strengthen the hair's shaft but if hair is getting too much then hair will become hard, brittle and difficult to manage which can cause breakage. It's important to follow up a protein treatment or protein damage with a moisture treatment, to soften and balance the hair.
A lot of times the ingredients won't simply say "protein," so How to tell if you're using too much protein?
Check out your hair care products and look for these words:
Placenta (Remember when people would tell you to use this stuff in your hair if you wanted it to grow?)
Products that are known for having Protein that I know of are some of the Organics Root Stimulator and Motions CPR products. I love Motions CPR and use these products on my hair once a month which helps a lot (I had no idea they were protein based so I guess it's a good thing I only use it once a month) but a follow-up moisture treatment is important.
To find out if you're hair lacks protein or has too much you can do a strand test.
Pull a strand of hair out from the root, don't break your hair! Hold it between your fingers, and pull slowly. If the hair stretches and breaks, then you need protein and moisture.
If the hair stretches and does not shrink back, you need protein.
If the hair stretches and shrinks back when you lessen the stretch, your hair has enough protein.
If your hair is suffering from too much protein don't worry, proceed to your nearest drugstore or beauty supply and get a non-protein conditioner and condition, condition, condition. Do conditioning washes, oil rinses, hair and scalp oilings, use moisturizing this and that, cholesterol treatments, etc until the issue is repaired. Messy, yes, but your hair will love you for it.