Phytophotodermatitis

A 25-year-old man presented to the dermatology clinic with reddish-brown streaks on his chest that had been present for several days. He was on no oral medications, and he had no relevant past medical history. He was concerned about the possibility of a skin infection.

History. Upon further questioning, he reported that he had been at a pool party 3 days previously. Out of concern for phytophotodermatitis, the patient was questioned at length about possible exposure to plant substances in combination with sun exposure. He reported that at the pool party, he had been on a pool float for hours while consuming several beers. He had placed lime wedges in the bottles, and he felt that the lime juice likely had leaked down the side of the bottles and onto his chest.

Diagnosis. Based on this history and the physical findings, the man received a clinical diagnosis of phytophotodermatitis.

Discussion. Phytophotodermatitis is an acute skin reaction that occurs following the combination of sun exposure and exposure to photosensitizing compounds found in plants. These photosensitizing compounds are found in many types of plants, including commonly contacted plants such as limes, lemons, celery, and parsley. The reaction may occur following contact with different parts of the plant, including the fruit, juice, stems, and leaves.

Furocoumarins are one type of photosensitizing plant compound and are isomers of psoralens. When combined with UVA radiation, they become phototoxic.¹ The reaction generates singlet oxygen and hydroxide radicals that directly damage epidermal cells and results in the acute development of erythema, edema, and sometimes bullae.² Hyperpigmentation sometimes may follow. This reaction is nonimmunogenic and does not require prior exposure to the plant.³

The most common plant families associated with the development of phytophotodermatitis include the Rutaceae, Umbelliferae, and Moraceae families. The Rutaceae family contains many citrus fruits, including limes, lemons, and grapefruits, as well as garden rue, a type of shrub. As in our patient’s case, many people have incidental exposure to the fruit or fruit juice, such as lime juice consumed with beverages. The Umbelliferae family contains carrot, celery, parsnip, and parsley plants. One common scenario is that of grocery store workers who develop this reaction following contact with celery. In the Moraceae family, the fig tree is a common trigger that may result in reactions in farmers who are exposed to its stems and leaves.⁴

The typical clinical presentation is that of painful erythematous plaques, often accompanied by bullae. This typically is followed by postinflammatory hyperpigmentation.^1,4 Clues to the diagnosis include unusual shapes or patterns of hyperpigmentation. The reaction typically occurs 12 to 48 hours after exposure to sunlight, although some patients presenting with hyperpigmentation do not recall the acute reaction.⁵

Phytophotodermatitis tends to occur more often in the summer months due to higher furocoumarin concentrations in the offending plants and due to patients’ increased exposure to sunlight.⁴ Groups at risk include those with recreational exposure, such as individuals returning from summer vacation, leading some authors to term the condition “Club Med dermatitis.”⁵ People in occupations at increased risk of phytophotodermatitis include grocery store workers, farmers, and bartenders who may come into contact with limes during drink preparation.

Awareness of the findings of phytophotodermatitis is essential, since the diagnosis is made clinically, and the skin findings often are misdiagnosed as allergic contact dermatitis, cellulitis, burns, or even child abuse.⁴

The acute reaction should subside within approximately 1 week following exposure, even without specific therapy.² Hyperpigmentation may persist for weeks to months but usually fades with time. Treatment of the acute reaction primarily is symptomatic and includes cold compresses and topical corticosteroids to reduce pain and duration of symptoms.⁴ For areas of hyperpigmentation, sunscreen should be used to prevent exacerbation.⁶

The most important aspect of therapy is patient education. Patients must be counseled to avoid the combination of phototoxic plant materials and sun exposure.

Outcome of the case. The patient was counseled on the diagnosis of phytophotodermatitis and advised to avoid further sun exposure to the area. The rash faded without further treatment after 3 weeks.

References:

1. Quaak MSW, Martens H, Hassing R-J, van Beek-Nieuwland Y, van Genderen PJJ. The sunny side of lime. J Travel Med. 2012;19(5):327-328.
2. Pathak MA. Phytophotodermatitis. Clin Dermatol. 1986;4(2):102-121.
3. Goskowicz MO, Friedlander SF, Eichenfield LF. Endemic “lime” disease: phytophotodermatitis in San Diego County. Pediatrics. 1994;93(5):828-830.
4. Bowers AG. Phytophotodermatitis. Am J Contact Dermat. 1999;10(2):89-93.
5. White W. Club Med dermatitis. N Engl J Med. 1986;314(5):319-320.
6. Weber IC, Davis CP, Greeson DM. Phytophotodermatitis: the other “lime” disease. J Emerg Med. 1999;17(2):235-237.