Phytophotodermatitis was described in 1942 by Klaber1 as a skin reaction to exposure to sunlight after previous contact with plants. It is caused by a phototoxic reaction to furocoumarins and anthraquinone derivatives. The plant species that most commonly induces this type of reaction is celery (family Umbelliferae), followed by lime and lemon (family, Rutaceae).

We present a series of 9 patients with similar clinical manifestations consisting of irregular homogeneous pigmentation on the dorsum of the hands (Figs. 1 and 2). The epidemiological characteristics of the patients are summarized in Table 1. Patients were aged between 14 and 41 years (mean [SD], 25.5 [9.8] years). The lesions were asymptomatic and there were no signs of eczema. A common finding in the history of all patients was the preparation of mojitos, with an interval of 7 to 14 days in the majority of cases between exposure and onset of the lesions. A curious finding was that none of the patients associated the onset of their lesions with the preparation of the mixture, and they were all surprised on being asked if they had prepared this drink in previous days.

Figure 1.

Asymptomatic, homogeneous hyperpigmentation that developed on the dorsum of the thumbs of both hands of a patient several days after preparing mojitos at a beach party.

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Figure 2.

Irregular hyperpigmentation that developed on the dorsum of both hands of a patient 3 days after serving mojitos at a wedding and followed by intense sunlight exposure in adjacent gardens.

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We propose the term “dorsal acropigmentation secondary to mojito preparation” to define a variant of occupational phytophotodermatitis or phototoxicity on the dorsum of the hands (Fig. 1) of waiters who prepare cocktails with lime, such as mojitos. This cocktail, ever more popular in Spain, is prepared with rum, sparkling water, mint, sugar, and lime. As this is not an immune reaction, no previous sensitization is required and anyone can be affected.

Lime-juice–induced phytophotodermatitis is well-known. This fruit, which belongs to the Rutaceae family, contains photosensitizing compounds, the main ones being bergapten and psoralen,2 with highest content in the skin of the fruit.3 The mechanism of phototoxicity observed with these furocoumarins has been described in detail. Typically, lime induces a phytophotodermatitis that presents acutely with erythema and the formation of vesicles at 12-36hours after exposure of the psoralen to UV radiation and is occasionally painful. The acute phase usually produces hyperpigmentation, depending on the case, but scarring is very rare. Onset of the dermatitis varies between hours and days after contact with the lime contained in the mojito and exposure to the sun. The cause of pigmentation may be melanocyte stimulation or a mechanism secondary to melanocyte damage that induces pigment incontinence.3 Symptomatic treatment is sufficient in most cases.

Some cases of lime-induced phytophotodermatitis have been associated with the custom of using lime when drinking certain types of Mexican beers.4 The fruit is used in cooking, though recently it has become very popular as an ingredient in certain cocktails, such as the mojito.5 In our patients, lime was the etiological agent of this phytophotodermatitis in amateur or professional bar staff who were exposed to sunlight after preparing mojitos, a Cuban drink invented during the era of Prohibition in the United States, when those who wanted to drink alcohol legally had to travel out of the country; Cuba became one of the favorite destinations.

The differential diagnosis and the medical history of these types of lesion should rule out contact with figs, lemons, geraniums, and St. John's wort, as other causes of phytophotodermatitis, and it is important to determine whether the person is involved in the preparation of mojitos, in an amateur or a professional setting. It must not be forgotten that, because of the polymorphism of this type of phototoxicity, there are numerous differential diagnoses, including Berloque dermatitis due to oil of bergamot contained in perfumes, frictional dermatitis, and even sexual abuse.6,7