Melanin pigments in blond hair
Q. I need to be enlightened on the subject of true blonde hair containing what type of melanin. In the past, I have learned that true blonde hair is composed of dispersed yellow pigments in low concentration. I have also learned that pheomelanins, which include the yellow and red pigments, do not bleach out while eumelanins (brown pigments) bleach easily. Therefore, how can true blonde hair be bleached out to the palest yellow stage, if it has yellow pigments? Thank you. Barbara, Pasadena, CA.
A. All human hair types at childhood contain the two types of melanin you mentioned. There is no hair type with only one type of melanin. Dark hair has a higher percentage (99%) of the brown pigment, eumelanin, and a much lower percentage (about 1%) of pheomelanin. Blonde hair still has about 95% of eumelanin and about 5% of pheomelanin. Of course dark hair has a much higher overall amount of melanin (eumelanin and pheomelanin) than blond hair.
Let us look at some numerical examples without putting much emphasis on the numbers because they are strictly hypothetical:
If we assume that a dark hair strand has 10,000 “molecules” of total melanin, then by the ratios above, 9900 “molecules” (99%) of these would be eumelanin and 100 “molecules” (1%) would be pheomelanin. In comparison, a blond hair strand of equal size may have only 100 “molecules” of total melanin. Of these, 95 “molecules” are eumelanin (95%) and 5 “molecules” are pheomelanin (5%).
When both dark and blond hair types are bleached, most of the accessible eumelanin in the two types of hair would be broken down and discolored, and only very little of the pheomelanin would do so. The reason why pheomelanin is harder to bleach is because it has sulfur linkages (or ties) that make the molecule more tightly packed and inaccessible to the bleach.
The end result is that dark hair lifts to a brassy undertone because of the significant amount of pheomelanin left behind (let’s say 90 molecules), while blonde hair reaches the palest yellow stage because only very few pheomelanins were there to start with, and they get even less after the bleach (Let’s say 3 or 4 molecules).
So the lesson to keep in mind is that all types of hair have both types of melanin, but the concentrations differ.