Protein Loss in Human Hair from Combination Straightening and Coloring Treatments

The study evaluated the protein loss in Caucasian virgin dark brown hair caused by combined chemical treatments of dyeing and straightening using the bicinchoninic acid (BCA) method. It was found that combining dyeing with sodium hydroxide-based straighteners resulted in a 356% increase in protein loss compared to virgin hair and 208% compared to only dyed hair. In contrast, the use of ammonium thioglycolate or guanidine hydroxide for straightening caused a smaller increase in protein loss, suggesting these as better alternatives for individuals who wish to combine both treatments. The study concluded that ammonium thioglycolate or guanidine hydroxide should be preferred for straightening when both treatments are desired.