A 43-year-old woman presented to the emergency department with a rash on her extremities that had started seven days earlier. She reported associated fatigue, subjective fever, and body aches.
The rash started shortly after spending a day at the lake with her cousin. They had mostly spent the day on a boat, but they had also gone swimming in the lake. She noticed the rash when she returned home that night, and she learned that her cousin had developed a similar rash.
She described the rash as burning and itchy. It was scattered on her hand and legs with flat, pink areas and some mild blistering. She had researched lake rashes and infections on the internet and become increasingly concerned that she may have had a serious skin or neurologic infection. She went to an urgent care center that told her to take Benadryl to see if it improved.
The patient noticed more lesions develop on her forearms and inner thighs over the next seven days. The rash also changed from its initial pink color to a darker brown. The burning and itching associated with the rash were improving, but she became increasingly nervous, developed body aches and subjective fever, and decided to come to the emergency department to have her rash and symptoms reevaluated.
She was afebrile and normotensive in the ED, and she appeared anxious. What was causing her symptoms?
Find the diagnosis and case discussion on the next page.
Phytophotodermatitis is a self-limiting dermatitis that occurs when the skin comes into contact with certain plant chemicals called photosensitizers that are activated by UVA light. Citrus, carrot, plants in the parsley family, and fig plants are the most common sources of this rash, and all of them contain the photosensitizing chemical furanocoumarins.
Patients initially present with areas of a red, itchy rash with a burning sensation. They may also have associated swelling if the rash is blistering and on the extremities or digits. A history of contact with a plant (limes, bergamot orange essential oil, figs, parsnip) and exposure to UVA light is important for making the diagnosis.
It may be necessary to observe the patient for improvement if there is a concern for cellulitis or another etiology of a blistering rash. The initial rash should be managed by decontamination with cold water and soap, and depending on severity, oral or topical steroids for treating the symptoms.
The rash will change from a red, blistering rash to hyperpigmented areas due to melanin deposition triggered by furanocoumarins. This hyperpigmentation can last for years, and patients should be referred to a dermatologist for appropriate long-term cosmetic treatment. In fact, fig and parsnip exposure was once used as treatment for vitiligo because of their hyperpigmentation effects.
Prevention is the most important first step with this rash. The rash requires the chemical and UVA light. Patients should know the local plants where they are and what not to touch. This is important for many other reasons besides this rash. They should also know that certain fruits like limes and oranges have chemicals that can trigger this reaction. They should decontaminate their skin if they touch these products and if UVA exposure is possible. And they should make sure their sunscreen blocks UVA light. This isn't perfect and skin protection with clothing and decontamination is best, but UVA sunblock does afford some protection.
After further discussion with the patient, it was discovered that she and her cousin had prepared margaritas on the boat that day. They did not wash their hands after this and did admit to getting some of the juice on their exposed upper legs (they were wearing bathing suits). The “new” lesions were not new but likely smaller areas that were not noticed until they became hyperpigmented.
The patient was concerned she may have been exposed to Naegleria fowleri or developed schistosomiasis. After reassuring her that her rash was not caused by an infection, was pathognomonic for a type of contact dermatitis activated by sunlight, and was sometimes known as margarita dermatitis or lime dermatitis, she was reassured and felt that her fatigue and body aches were likely due to a lack of sleep from worrying.
This case highlights the importance of taking a full history from patients (especially those with rashes), knowing the difference between benign and malignant rashes, and the importance of reassuring patients if they have benign diagnoses and facilitating follow-up in an age of online medical information that can be understandably misinterpreted because they are not medically trained.
Dr. Pinkstonis an assistant professor of emergency medicine at Denver Health and University of Colorado Hospital.