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
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
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