Berloque dermatitis

Did You Know?

• Phytophotodermatitis is not an immunologic response; no prior exposure to the photosensitizing agent is required.
• The carrot family Apiaceae accounts for approximately half of all plant species reported to induce phytophotodermatitis.
• In children, phytophotodermatitis has sometimes been mistaken for child abuse.

Signs and symptoms

A reaction typically begins within 24 hours of exposure and peaks at 48–72 hours. Initially, the skin reddens and itches or burns. Large blisters may form within 48 hours, and the affected areas can develop black, brown, or purplish hyperpigmentation that may last for years. This pigmentation is caused by melanin production triggered by furanocoumarins. The condition can affect people of any age.

Causes

Berloque dermatitis is caused by contact with bergamot oil, which contains bergapten, a linear furanocoumarin. Bergapten gets its name from the bergamot orange. The photosensitizing substances belong to the furanocoumarin class, activated by long-wavelength ultraviolet (UV-A) light. The most toxic of these are linear furanocoumarins, such as bergapten and xanthotoxin. The citrus family Rutaceae is the second most widely distributed plant family associated with phytophotodermatitis. Numerous citrus fruits in this family exhibit phototoxic effects, with lime being the best known. Phytophotodermatitis from limes is sometimes called 'lime disease,' distinct from Lyme disease.

Prevention

The first line of defense is to avoid contact with phototoxic substances. Avoid contact with citrus fruits and other biological agents known to have phototoxic effects. Do not incinerate phototoxic plants, as this disperses the substances. In outdoor situations where contact is likely, wear long trousers, a long-sleeve shirt, gloves, and protective eyewear. If protective clothing is unavailable, apply sunscreen to exposed areas. After outdoor activity, shower or bathe as soon as possible, wash clothing, and then wash hands. If contact occurs, immediately wash the affected area with soap and cold water, and avoid sunlight for at least 48 hours. Stay indoors if possible, avoiding light through windows. If staying indoors is not possible, cover the area with sun-protective clothing or apply sunscreen. Phytophotodermatitis is triggered by UVA light in the 320–380 nanometer range, so products should block these wavelengths.

History

People have known about plants that make skin sensitive to light for thousands of years. Around 2000 B.C. in Egypt, the juice of Ammi majus was applied to vitiligo patches before patients went into the sun. In A.D. 50, the Greek physician Dioscorides noted that fig leaves could restore pigment to vitiligo. The first modern report of plant-caused dermatitis came from Chaumton in 1815, who described how cow parsnip sap could inflame and ulcerate skin. In 1887, Sornevin reported similar effects from Heracleum sphondylium, but neither understood that sunlight was necessary. The term "berloque dermatitis" was introduced in 1925 by Rosenthal for the pendant-like streaks of pigmentation on the neck, face, and arms. He did not know that in 1916, Freund had already correctly linked these streaks to sun exposure after applying Eau de Cologne, a perfume made with bergamot oil. That oil contains bergapten, a linear furanocoumarin named after the bergamot orange.