Research on hair discoloration, conducted since the 1970's, has revealed that hair of various colors can change tone due to disease, chemicals and medications. Studies pinpointed copper trace elements, which are commonly found in pool water or piping, as the culprits that turned light and dark-colored hair green. They also found that heavy smokers were not only prone to premature graying, but that the de-pigmented hair could be further affected by tar residues in the air, causing it to turn yellow. For non-smokers with gray, white or silver hair that is yellowing--a condition referred to as xanthotrichla--research shows certain scalp medication and topical skin creams are a likely cause.
A study published in the Journal of Drugs in Dermatology showed that xanthotrichla was caused by an exogenous chemical, that is, a drug derived from outside of the body. Selenium sulfide, a topical drug commonly known by the brand name Selsun Blue, is available in shampoo, lotion and foam form and is used on the scalp to treat dandruff and seborrheic dermatitis, according to Drugs.com.
Selenium sulfide occurs in dosages of one and 2.5 percent, with the latter strength available only by prescription. The study reported the case of an 86-year-old non-smoker using 2.5 percent selenium sulfide shampoo. His white hair turned yellow after two months of use, and resumed to white after discontinuing use for just a few days. The study did not definitively name the mechanism in selenium sulfide that caused the yellowing, however, they theorized that the over-depositing of the yellow-red colored chemical onto the hair shaft had to do with it.
Dihydroxyacetone (DHA) is the active ingredient in sunless tanner that temporarily stains and tints the outermost skin cells to a darker tone. The chemical is approved by the FDA and carries fewer health risks than any other tanning method available, according to DermNetNZ.org. DHA tanning solutions can be applied as lotions or misted onto the body and are typically available in concentrations between three and five percent. Another patient in the study from the Journal of Drugs in Dermatology reported that his mustache became a yellowish hue after using Neutrogena's Summer Glow self-tanner. Because he wanted to continue self-tanning, he didn't discontinue use and researchers weren't able to see if the yellow hue dissipated as a result. However, they did conclude that those with white or gray hair should be warned of this adverse affect from DHA-containing products.
Another primary source of yellow hair shaft discoloration is the chemical dithranol, which is found in the psoriatic topical medication anthralin, according to the Journal of Drugs in Dermatology research study. The skin cream slows the production of skin cells, according to Drugs.com. Dithranol has been used to treat psoriasis for over a century and is derived from Goa powder in the arroba tree, according to BeatPsoriasis.com. It is a yellow cream that easily stains skin and hair, with hair discoloration being only one of its many side effects.