A 43-year-old woman presented to the emergency room 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 his 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 got home that evening and learned that her cousin had developed a similar rash.
She described the rash as burning and itchy. It was strewn all over her hand and legs with flat, pink areas and slight blisters. She had researched lake rashes and infections on the internet and was increasingly concerned that she had had a serious skin or neurological infection. She went to an urgent care center who told her to take Benadryl to see if it got better.
The patient noticed more lesions developing on her forearms and inner thighs over the next seven days. The rash has also changed from its initial pink color to a darker brown. The burning and itching associated with the rash was improving, but she became increasingly nervous, developed body aches and a subjective fever, and decided to go to the emergency room to have her rash and symptoms reassessed.
She was afebrile and normotensive in the ER, and she seemed 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 fruits, carrots, plants in the parsley family, and fig trees are the most common sources of this rash, and all contain the photosensitizing chemical furanocoumarins.
Patients initially present with areas of red, itchy rash with a burning sensation. They may also have associated swelling if the rash is blistered and on the extremities or fingers. A history of contact with a plant (linden, essential oil of bergamot, figs, parsnips) and exposure to UVA rays is important for making the diagnosis.
The patient may need to be observed for improvement if there is a risk of cellulitis or other etiology of a blistering rash. The initial rash should be managed with cold water and soap decontamination and, depending on severity, oral or topical steroids to treat 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, exposure to figs and parsnips was once used as a treatment for vitiligo due to their hyperpigmentation effects.
Prevention is the most important first step with this rash. The eruption 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 be aware that certain fruits like limes and oranges contain chemicals that can trigger this reaction. They must decontaminate their skin if they touch these products and if UVA exposure is possible. And they need to make sure their sunscreen blocks UVA rays. It’s not perfect and skin protection with clothing and decontamination is best, but UVA sunscreen does provide some protection.
After further discussion with the patient, it was discovered that she and her cousin had made margaritas on the boat that day. They didn’t wash their hands afterwards and admitted to getting juice on their exposed thighs (they were wearing bathing suits). The “new” lesions were not new, but likely smaller areas that weren’t noticed until they became hyperpigmented.
The patient feared that she had been exposed to Naegleria fowleri or developed schistosomiasis. After reassuring her that her rash was not caused by an infection, that it was pathognomonic for a type of sunlight-activated contact dermatitis and was sometimes known as margarita dermatitis or lime dermatitis, she was reassured and felt that her fatigue and body aches were probably due to lack of sleep from worrying.
This case highlights the importance of taking a complete patient history (especially those with rashes), knowing the difference between benign and malignant rashes, and the importance of reassuring patients if they have benign diagnoses and facilitate follow-up in the era of e-medicine. information that can be misinterpreted in an understandable way because they have no medical training.
Dr. Pinkstonis Assistant Professor of Emergency Medicine at Denver Health and University of Colorado Hospital.