Egg protein is commonly cited as beneficial for hair health due to its rich content of essential amino acids, vitamins, and minerals. Scientifically, hair is composed primarily of keratin, a protein, and thus adequate protein intake is necessary for healthy hair growth and maintenance. Dietary egg protein provides amino acids like cysteine and methionine, which are important for keratin synthesis. Several small studies have indicated that protein deficiency can lead to hair thinning or loss, and protein supplementation may help reverse these effects in deficient individuals. However, there is limited direct scientific evidence showing that consuming egg protein leads to improved hair health in individuals without a deficiency. Most research supports the idea that a balanced diet with sufficient protein supports overall hair health, but does not specifically endorse egg protein over other protein sources.

In addition, topical application of egg-based hair masks is a traditional practice, but there is minimal clinical evidence supporting efficacy for hair strength or growth. Most benefits are anecdotal or based on the known conditioning properties of proteins when applied to hair fibers, rather than true biological effects on hair follicles.

In summary, while scientific rationale exists for adequate protein intake supporting hair health, direct evidence specifically promoting egg protein for hair is modest. Thus, the evidence rating is 2 out of 5.