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Phytophotodermatitis due to puncture from lime tree thorn.

To the Editor: Phytophotodermatitis is a cutaneous phototoxic inflammatory eruption due to exposure to light-sensitizing botanical substances and longwave ultraviolet radiation that usually begins approximately 24 hours after exposure and peaks at 48 to 72 hours. (1) The primary skin lesions of phytophotodermatitis may range from delayed erythema (24-48 h) to a frankly nodular eruption. The photosensitizing compounds in the plants are furocoumarins. The phototoxic reaction is entirely independent of the immune system; thus, prior sensitization or an intact immune system is not required. The clinical history is essential in establishing the diagnosis of phytophotodermatitis.

While picking limes from a Tahitian lime tree located in the Paradise Park area of Kea'au, Hawaii, a 69-year-old Caucasian man developed phytophotodermatitis after puncture of the skin in the right scapular area by a thorn. The patient's back was exposed to the sun the following day. Lesions first developed slightly more than 24 hours after the initial injury and peaked at 36 hours. Three large, red, raised lesions were observed, and two had central vesicles. Following symptomatic treatment with 2% diphenhydramine spray and triple antibiotic ointment (bacitracin, neomycin, and polymyxin B), beginning resolution of the lesions was noted by the same evening, and complete resolution occurred over a week's time. There was no pruritus or residual cutaneous hyperpigmentation. The past history was negative for asthma, hay fever, or allergic reactions to medications.

The present case had some unusual features. The patient had an asymptomatic lime thorn scratch over the right forearm, whereas the central scapular lesion developed after a puncture wound from the lime thorn, and the satellite scapular lesions apparently resulted from spread due to scratching by the patient. This suggests that more of the irritating substance was introduced through the puncture.

The onset of dermatitis is variable, however, and may begin within a few hours to days after exposure. (2) Recent evidence supports it being a type of irritant contact dermatitis. (3,4) The sap of the tree and scratches by the thorns may cause rashes in sensitive individuals. A variety of reactions have been noted as a result of exposure to citrus peel. (5) Many plants, including limes, contain furocoumarins (psoralens) that cause phytophotodermatitis by forming phototoxic compounds on exposure to ultraviolet A radiation. (3,4) After resolution of the phototoxic reaction, postinflammatory hyperpigmentation may occur.

Phototoxic reactions to exposure to lime can be polymorphous in nature. Due to the bizarre configurations of lesions induced by phytophotodermatitis, it can be confused with many other diseases, especially in children. (2) A detailed clinical history is crucial in establishing the correct diagnosis of phytophotodermatitis. The treatment of acute phytophotodermatitis is primarily symptomatic with the lesions responding well to the application of topical corticosteroids and cold compresses. (2) Mild cases may not require treatment.

Lawrence M. Roth, MD

Department of Pathology

Indiana University School of Medicine

Indianapolis, Indiana

Elizabeth H. Levin, MD

Department of Psychiatry

UMDNJ--Robert Wood Johnson Medical School

Camden, New Jersey

Arthur H. Schwartz, MD

Retired Professor of Psychiatry

UMDNJ--Robert Wood Johnson Medical School

Piscataway, New Jersey

David J. Roth, BA

Jerusalem, Israel


1. Baugh WP, Barnette D Jr. Phytophotodermatitis. emedicine [August 24, 2005; Accessed March 1, 2006].

2. Goskowicz MO, Friedlander SF, Eichenfield LF. Endemic 'lime' disease: phytophotodermatitis in San Diego County. Pediatrics 1994;93:828-830.

3. Nigg HN, Nordby HE, Beier RC, et al. Phototoxic coumarins in limes. Food Chem Toxicol 1993;31:331-335.

4. Wagner AM, Wu JJ, Hansen RC, et al. Bullous phytophotodermatitis associated with high natural concentrations of furanocoumarins in limes. Am J Contact Dermat 2002;13:10-14.

5. Solis RR, Dotson DA, Trizna Z. Phytophotodermatitis: a sometimes difficult diagnosis. Arch Fam Med 2000;9:1195-1196.
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Title Annotation:Letters to the Editor
Author:Roth, David J.
Publication:Southern Medical Journal
Date:May 1, 2007
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