Plants can cause mild to severe skin reactions, dermatologist warns

Common vegetation can cause rashes, hives and even severe internal swelling, but most of these reactions can be avoided with simple preventive measures, Julian J. Trevino, MD, FAAD, said in a presentation at the 69th Annual Meeting of the American Academy of Dermatology in New Orleans.

Most people experience mild reactions at the point of contact with the plant, but certain people with allergies or sensitive skin that is prone to eczema or atopic dermatitis may experience severe or longer-lasting effects that will require medical attention.

When brushed up against, stinging nettle plants release histamine or acetylcholine that cause toxin-mediated urticaria within 30 to 60 minutes after exposure. In most cases, the hives resolve on their own within a few hours, Trevino said in a press release.

Julian J. Trevino

Immunologic contact urticaria is a more severe type of hive outbreak that occurs in those with eczema or who regularly handle fresh fruits and vegetables, herbs, nuts shrubs and grasses. Immunologic contact urticaria has been known to causes swelling in the throat, lungs or gastrointestinal tract — conditions that require immediate medical attention.

The spines and glochids of certain cacti or prickly pear plants are another source of skin irritation. Because the spines may break the skin, they carry the risk of an additional bacterial or fungal infection, Trevino said.

“The spines from the plants should be carefully removed from the skin, usually with tweezers or a piece of tape that is placed over the area where the spine entered the skin and gently torn away with the tip of the spine attached,” he said in the release. “Minor itching, irritation or rash can be typically treated with an oral antihistamine or over-the-counter topical steroid, but when a rash doesn't respond to over-the-counter treatments, you should see a dermatologist. In cases where a rash is accompanied by more severe reactions, such as difficulty in breathing or swallowing, a person should go to the emergency room immediately.”

Some of the most well-known irritating plants — poison ivy, oak and sumac — contain a resinous sap called urushiol that causes a rash on the 50% of the population who is allergic to these plants.

“When a poison ivy plant is injured in any way, the urushiol is released quickly and can stick to anything around it,” Trevino said in the release. “That means that you can develop poison ivy if you pet your dog after he has come in contact with the plant, or if you touch a gardening tool or piece of clothing that has come in contact with poison ivy. Even airborne contact with urushiol is possible, especially in the fall or winter when these poisonous plants are burned among other brush and particles of urushiol are released into the air. If these airborne particles land on your skin or you inhale them, you can get a widespread rash and severe irritation in the respiratory tract.”

When skin makes contact with urushiol, reactions can be minimized by immediately washing the area of contact with water, Trevino said. To treat the rash, he recommended lukewarm baths with products containing aluminum acetate, or tropic calamine lotion or steroids. Oral antihistamines can be helpful, although topical ones should be avoided because some people are allergic to them.

A patient with a severe rash that does not dissipate with OTC medications may require topical or oral steroids, according to Trevino.

To minimize the risk of such skin reactions, he recommended the following tips with patients:

Wear protective clothing whenever possible — including gloves (preferably vinyl gloves), long sleeves and long pants tucked into socks.
Apply an OTC barrier cream or lotion containing quaternium-18 bentonite to exposed skin before going outdoors. This helps prevent urushiol from poisonous plants from contacting the skin.
Avoid poisonous plants (remember this phrase: “Leaves of three, let it be”).

Disclosure: Dr. Trevino reports no relevant financial disclosures.