Warmer weather brings a different set of skin health issues than those we see during the cooler months. Your skin can be damaged by sunburn, assaulted by flying insects, or, if you enjoy working in the garden, hiking, or camping, come into contact with poisonous plants.

Poison ivy, poison oak, and poison sumac are three commonly found plants whose oil, known as urushiol (you-ROO-shee-all), is known to cause allergic contact dermatitis, a type of rash that results from an allergic reaction at the site of exposure.

Many individuals will develop a rash when urushiol makes contact with their skin. The reaction can vary from a mild rash and itching to a more severe response with blistering and swelling.

The best way to avoid getting poison ivy, oak, or sumac is to learn how to identify each of these plants. The old saying, “leaves of three, let it be,” is a good place to start, although some species of these plants have more than three leaflets.

Poison Ivy

Poison ivy can grow as ground cover, a low shrub, or a vine that climbs trees. It is found across most of the United States, and it’s what many of us in the Northeast are familiar with.

The leaves initially appear solid green in clusters of three per stem. They can be dull or glossy with pointed tips, and the thin aerial roots give the vines a fuzzy look. In summer, poison ivy plants produce yellow-green flowers, followed by whitish berries. In the fall, the leaves turn yellow and red.

Poison Oak

Poison oak leaves closely resemble regular oak leaves, typically growing in clusters of three. However, some varieties of poison oak can have five, seven, or nine leaves per cluster. Poison oak generally grows as a shrub and is most commonly found in the Southeast or on the West Coast. It produces clusters of greenish, yellow, or white berries.

Poison Sumac

This plant prefers to thrive in swampy areas and generally has seven to thirteen leaflets arranged in pairs. The leaves sometimes display black or dark brown spots. In the fall, the leaves change to red, yellow, and pink hues. Poison sumac develops into a woody shrub with glossy, cream, or pale yellow berries.

How is the urushiol oil transferred to the skin?

The urushiol oil in poison ivy, oak, and sumac is found in the leaves, stems, and roots of these plants. You don’t have to touch them directly to get the oil on your skin; it can be carried on the coats of pets or gardening tools, which may transfer to you. Once exposed, the oil is quickly absorbed into the body through the skin.

After your first exposure, the rash might take up to a week to develop, while subsequent exposures can appear within 12 to 72 hours. It may not show up all at once, but it can emerge in different areas over several days, leading people to believe the rash is spreading.

It is a myth that the rash spreads through the fluid in the blisters; direct contact with the urushiol oil causes the rash to develop. If the oil is on your skin, the rash can spread to other areas of your body through contact, such as scratching or rubbing.

Please remember that you should never burn any parts of these plants, as the smoke can carry urushiol oil into your nose, throat, and respiratory system, potentially leading to more serious health issues.

What to do if you’ve been exposed

If you suspect that you have been exposed to poison ivy, oak, or sumac, wash your skin with soap and warm water as soon as possible and scrub under your nails with a brush. The oil can cling to many surfaces, such as gardening tools, golf clubs, and your pet’s coat, remaining active for over a year. Therefore, be sure to rinse your pet’s coat and wash any tools or objects with warm, soapy water. Contaminated clothing should be washed separately in hot water with detergent, and remember to rinse your washing machine thoroughly to eliminate all traces of the oil.

If you develop symptoms, taking short, lukewarm baths can help soothe the skin. Oatmeal baths may also relieve the itch. Avoid scratching the skin or breaking the blisters, as this can increase the itch sensation and the risk of infection.

Cool compresses, hydrocortisone cream, and calamine lotion are treatments you can find at your local pharmacy and use safely at home. If the itch keeps you awake at night, consider trying an over-the-counter antihistamine, such as cetirizine or diphenhydramine.

You should seek medical attention if you experience any of the following conditions:

• If you have trouble breathing or swallowing, call 911 or go to the nearest hospital emergency room.
• Contact your healthcare provider’s office if:
  • The rash affects your face (especially your eyes) or genital area.
  • The rash covers a large area of your body.
  • You are unable to adequately control your symptoms at home.

Your healthcare provider may prescribe a topical steroid cream or ointment, which might need to be used for 10 to 14 days, as that is typically how long you can expect the rash to last. Oral steroids are prescribed in very severe cases or when your vision is at risk.

If you work outdoors and are frequently at risk of exposure, consult your healthcare provider or dermatologist about over-the-counter skin products that contain a barrier, such as bentoquatam, to help protect your skin from urushiol. For everyone else, before heading outside, learn to identify these pesky plants!

This article has been reviewed by Dr. Jack Krushell, Chief of Dermatology at Atrius Health