Scientists first discovered canthaxanthin, a common yellow carotenoid pigment, in edible chanterelle mushrooms. The chemical also occurs naturally in crustaceans, carp, green algae, Pacific salmon, and golden mullet. Considered a coloring agent and an antioxidant, canthaxanthin is approved by the United States Food and Drug Administration (FDA) as a food additive, in which case only minute amounts are employed.
Some tanning pills incorporate this pigment, which, when ingested, accumulates in the fat layer of the skin and produces a golden hue, simulating a tan. Although canthaxanthin theoretically increases skin resistance to ultraviolet light due to its antioxidant effects, the FDA does not approve the use of this product as a tanning agent or a medicine. The copious amount required to induce a skin-coloring effect has been linked to several side effects, including liver damage, aplastic anemia, and canthaxanthin retinopathy, an ocular condition in which yellow deposits collect in the retina.
Researchers have studied canthaxanthin for use in treating conditions that produce abnormally high levels of irritation and sensitivity to sunlight, including medication-induced photosensitivity, eczema, and erythropoietic protoporphyria, which is a genetic disorder. During the warmer months when patients most often receive more sun exposure, physicians prescribe between 60 to 90 milligrams of canthaxanthin each day. Patients typically use the pills three to five months each year.
Due to its chemical similarity and possible conversion to Vitamin A, patients with allergies to Vitamin A or carotenoids should not take this product. Canthaxanthin is soluble in fat and can be stored in the body for long periods of time. For this reason, as well as its unknown effect on a developing fetus, pregnant women and breast-feeding mothers should refrain from using these pills.
Canthaxanthin can produce unpleasant adverse reactions, including diarrhea, nausea, stomach cramps, and reddish-orange body secretions. It may also lead to the development of an itchy, dry skin rash, known as urticaria, or hives in allergic individuals. Aplastic anemia, a dangerous and potentially fatal condition in which the bone marrow fails to make new blood cells, can occur with the use of these carotenoid pills. Reported in 1989, tanning pill intake induces the reversible deposition of yellow crystals in the retina of the eye, associated with reduced ability of the light-sensitive cells to detect light at lower levels. Considering the potential for liver toxicity along with the other drawbacks of this additive, the FDA issued a health warning in 2003 to all companies that marketed products containing this chemical.