Q. My son suffers with rashes to poison ivy when vacation at the lake. Is this an allergy?
Dr. Skotnicki: The rash you get from touching poison ivy is an allergic response to the plant’s resin, which is called urushiol. A poison ivy reaction is called allergic contact dermatitis. It will usually appear about 24 hours after exposure. The skin symptoms can range from being mildly red, swollen and itchy – to severe vesicles (bubbles of liquid) and large blisters.
This is an allergy that’s quite common. However, it is a specific immune response and not every person who touches this plant will react. Repeat exposure to poison ivy can lead to sensitization and a lifelong allergy. With each contact the poison ivy allergic reaction can become worse, leading to increasingly severe dermatitis.
The allergy is not life-threatening, but it certainly can be uncomfortable.
Identifying the Ivy
The best way to treat poison ivy allergic contact dermatitis is avoidance. It’s important to be able to identify the plant (knee height, with three green, pointed leaves, which turn red in the fall). Once identified, someone who is not allergic should remove it from areas close to your home or cottage.
Importantly, never burn the poison ivy plant, as the allergen can become airborne.
There is also a product available online called Ivy Block, which acts as a shield against poison ivy, poison oak and poison sumac by physically blocking contact with their resin. It will not treat the rash, but it is a preventative barrier.
If your son does get allergic contact dermatitis from exposure, treat it with cool water compresses followed by application of a prescription-strength hydrocortisone cream (see your doctor).
An antihistamine can help with the itch, but it won’t improve the dermatitis.
Post last updated: June 2021Submit a Question View all posts by this medical expert.