Summer is finally here, and Mother Nature is calling you outside. Long walks in nature, trips to the local forest preserve, and destination hikes are all enticing options, but danger could be lurking in that low-lying shrub or bush featuring clusters of three glossy leaves.

Poison ivy contains an oily resin called urushiol that causes an allergic reaction in about 80 to 90 percent of people. Urushiol is extremely potent: Just 50 micrograms, less than a grain of salt, is enough to cause an itchy, blistery rash that usually has a streaky or patchy appearance. The rash appears a day or two after exposure to the oil.

The exception is your very first exposure, which rarely causes a reaction. It primes the immune system to respond to subsequent urushiol exposures in a way that’s similar to how a vaccine trains your body to attack a certain virus.

Know what to avoid

Start with the simple adage, “Leaves of three, let it be.” Poison ivy always has a trio of three pointed leaves that may be smooth-edged or jagged, shiny or dull. They start out red in the spring and turn yellow, red, or orange in the fall. White berries or greenish-white flowers may be present. The roots of the plant often climb trees and look like thick, hairy vines. Every part of the poison ivy plant, from the leaves to the roots, contains urushiol, even when dead.

If you’re not sure whether you’ll be near the toxic plant, wear long sleeves and pants, taking care to tuck them into your socks. When gardening or doing yard work, wear heavy-duty gloves and wash them, your clothes, and your tools afterward. Dogs and cats aren’t allergic to poison ivy, but the resin can live on their fur, so if you think that the two of you have been exposed, give your pet a bath, wearing rubber gloves to protect yourself.


If you do brush against the plant, wash up as quickly as possible. Getting the oil off your skin as soon as you’ve been exposed can prevent the rash from ever developing. You can use regular soap and water, but a recent article published in the Journal of the American Academy of Dermatology reported that dishwashing soap may be a smarter choice, thanks to its ability to break down oil.

Use a washcloth and forcefully rub any affected areas in one direction only, rather than back and forth, using hot water. Rubbing alcohol can also work. Consider carrying alcohol wipes with you on walks.


If you don’t get the oil off quickly enough to prevent the rash, you’re looking at about a week or two of itching. For mild cases, do-it-yourself treatments like soothing oatmeal baths and cool, wet compresses applied to affected areas three to four times a day for 20 minutes may be enough to ease the itch. Over-the-counter topical treatments such as hydrocortisone cream or calamine lotion may help, as can non-sedating oral antihistamines such as loratadine (Claritin) fexofenadine (Allegra), or cetirizine (Zyrtec) during the day or diphenhydramine (Benadryl) at bedtime. More severe cases and rashes around the eyes may require a course of prescription oral steroids, sometimes lasting for up to three weeks. Your primary care physician or dermatologist can prescribe these. Some doctors may be tempted to prescribe a quick five-day course of oral steroids, but poison ivy cases have been known to rebound with too short of a course.

Resist the itch

Some scratching is inevitable, but do your best to avoid it as much as you can, especially if you have blisters. While the poison ivy rash is not contagious (see sidebar), bacteria on your hands could cause an infection called impetigo that is. Impetigo shows up as itchy red sores that break open, releasing a thick yellow fluid that forms a honey-colored crust. If you notice this happening, see your doctor, as you may need a topical or oral antibiotic.

If you can’t control the scratching and a blister does break open, keep the area clean and apply an ointment like petroleum jelly to protect the skin. Do not apply an over-the-counter antibiotic ointment, which itself can cause contact dermatitis.

Poison oak and poison sumac

Urushiol is also found in poison oak and sumac. The leaves-of-three adage doesn’t work with these plants. Poison oak’s hairy leaves can also be in groups of five or seven, while poison sumac leaves grow in clusters of seven to 13 leaves. Urushiol is in cashew shells and mangoes, too. In fact, previous exposure to poison ivy can predispose a person to developing an allergic reaction called mango dermatitis, characterized by tingling, redness, and itching in and around the mouth.

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