For the love of color: Plant colors and the dermatologist.

Humans have been anointing their skin with natural colorants since antiquity. Before the advent of modern cosmetics, tattoos and hair dyes, the spectacular colors in plants served as a palette for humanity's fascination with color. Skin, hair, nails, teeth and clothing have been altered with botanical colorants for centuries. Understanding the relevance of botanical colorants is an important part of cultural competency. Substitution or adulteration of plant colorants with synthetic colorants has played a role in varied dermatoses (eg. black henna, kumkum, and Holi dermatoses). Safety concerns over synthetic colorants have led to a resurgence of natural colorants. However, some plant colorants have produced adverse reactions. Plant colorants have also played an integral role in medicine. Ingested plant colorants are an indispensable part of our diet, playing crucial roles in the maintenance of health and prevention of disease. Excessive intake of some pigments can alter skin color (carotenoderma, lycopenemia, and the golden tan of canthaxanthin). We have relied on the colors of hematoxylin and alizarin red, derived from the logwood tree and madder roots, respectively, to study and diagnose disease in pathology. We briefly review the uses, cultural relevance, and adverse effects of the common botanical colorants on the skin, hair, and mucosa. We also describe their relevance in our diet, and in the diagnosis and description of dermatological diseases.