What Is Phytophotodermatitis?

Phytophotodermatitis is a reaction to sunlight that occurs after exposure to some plant substances. Not all patients will develop a skin reaction after handling certain plants and spending some time in the sun, but those that do may experience bruising, rashes, and blisters. This condition does not involve the immune system and thus doesn't behave like contact dermatitis and other allergies. It can appear at any age and in people without any known sensitivities.

Two separate exposures are required in phytophotodermatitis. The first is handling a plant substance known to cause photosensitivity, like citrus juice or turnips. This material soaks into the skin, and when the patient goes out into sunlight, a chemical reaction can occur. The reaction causes skin inflammation and irritation. Patients may not initially notice a problem, as it can take several hours for the reaction to manifest.

One issue with phytophotodermatitis is that it can sometimes look like abuse. The marks often take the form of hand prints because a common source of exposure is touching the body after handling plant materials, or being touched by a friend or family member. A child helping a parent make a lemon meringue pie, for example, might be streaked with lemon juice from the parent's hands. This later causes the appearance of livid hand prints, which may understandably be taken as a sign that the child was slapped or grabbed.

Patients who develop photosensitivity after exposure to certain plants can use topical creams to address the irritation and promote skin healing. They need to be careful about cooking and interacting with plants on hikes and other outdoor activities. Wearing gloves and washing the hands thoroughly can help reduce the risk that plant compounds will soak into the skin and cause phytophotodermatitis.

The same compounds that become an issue in phytophotodermatitis can sometimes be useful for medical therapies. Psoralens are a common culprit. These compounds are used in a form of therapy for some skin conditions, where patients take medication to sensitize their skin before a session of ultraviolet A radiation to treat skin lesions.

Parents who know their children have sensitivities of this nature may want to consider putting a doctor's note on file with care providers and at the school. When marks are observed on a child, the note can clarify matters and prevent mistaken reports of child abuse. It can also be helpful to carry such letters, in the event a police officer or social worker notices what appear to be signs of abuse on a child.