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poison ivy
Poison ivy is an allergic contact dermatitis caused by urushiol, an oil found in poison ivy, poison oak, and poison sumac plants. The feet and lower legs are especially vulnerable because they often come into contact with vegetation during outdoor activity.
Urushiol triggers an allergic reaction in most people, though a small percentage of the population is naturally immune. The rash can develop from direct contact with the plant, touching contaminated objects such as clothing or pets, or exposure to airborne particles—especially when plants are burned. The oil can remain active on surfaces for years, making re‑exposure common if items are not thoroughly cleaned.
Early signs appear within 12–48 hours and include small red bumps that may progress to blisters, intense itching, and oozing. Treatment focuses on reducing inflammation and preventing secondary infection. Prescription‑strength topical cortisone is most effective, while over‑the‑counter hydrocortisone or calamine lotion can offer mild relief. Cool showers, oatmeal or baking‑soda baths, and oral antihistamines may help ease itching and discomfort.
Prevention is key. Learning to identify the plants—“leaves of three, let them be”—wearing protective clothing, and washing exposed skin within 15 minutes can significantly reduce the risk of a reaction. All clothing and gear must also be cleaned to remove lingering urushiol.
Reviewed by: Medical Review Board
WHAT IS POISON IVY
Poison ivy can occur anywhere on the body but does have a high predilection for the feet and lower legs. It is generally regarded that this rash is easier to avoid than it is to treat. The best way to avoid it is to become an amateur botanist.
Be aware that it is the oil in the plants that cause the rash. This oil is known as urushiol. Exposure to the oil creates a contact dermatitis which is an allergic reaction. Fifteen to thirty percent of the population are immune to the effects. Compare poison ivy to eczema
Below is a picture of this type of dermatitis.
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The rash can develop from:
- coming in direct contact with the leaves of the poison ivy plant
- coming in contact with something that has touched the plant (dog, sports equipment, clothing, etc.)
- particles in the air from the poison ivy plant coming in contact with your skin may set off a reaction. That is why it is recommended that you never try to destroy these plants by burning them.
Urushiol oil can remain viable on dead plants and other surfaces for up to five years causing the same skin reaction.
The saying “leaves of three, let them be” will be mentioned in any article on this type of dermatitis. Learn to recognize that three leaved, low to the ground plants may very well be poison ivy. Three-leaved poison oak also grows as a low plant or bush; their leaves resemble oak leaves.
Poison sumac bushes or trees are more common in wet, marshy areas, the difference in the leaves is that each leaf has seven to thirteen shiny, smooth edged leaflets.
If you know you are going to be in an area with poison ivy and incidental contact is a possibility then the best way to protect yourself is by wearing long pants, tucked into your socks, along with a long sleeve shirt. Some sources recommend spraying exposed body parts with deodorant as there is an additive in the deodorant that prevents the poison oil from entering the skin.
Once exposed to the urushiol oil try to wash off the oil with nothing more than soap and water within fifteen minutes or less. If available, lye soap may work somewhat better.
The problem with urushiol oil is that it remains active for a long period of time. All clothing and equipment that came into contact with the oil also has to be cleaned since any lingering oil can also re-infect.
Once you are exposed, a rash will develop in one to two days. At this point treatment is geared to reducing symptoms and preventing blistering and secondary bacterial infection.
TREATMENT OF POISON IVY
In around 12 hours after exposure the first signs will be little bumps that look like insect bites.
Prescription grade topical cortisone cream applied to the area in an effort to reduce the impending inflammation is the best treatment available. Just apply the medicine, allow to air dry. Do not cover with bandages. If prescription cortisone cream is not available to you than over-the-counter hydrocortisone cream or calamine lotion is an acceptable alternative, but still not as effective as prescription medication.
Oral antihistamines may be very helpful to reduce the itch. By scratching the area you increase the inflammation, you may also spread the poison and you may develop secondary bacterial infections due to the breaks that will occur in the skin. This will then require oral antibiotics.
Cool showers and lukewarm baths with oatmeal or baking soda added to the baths may be helpful in reducing the inflammation and drying up the oozing blisters.
The good news is that this condition is a self limiting usually resolving in 14 days, and that during the active phase, any measures you take to reduce the inflammation and itching will go a long way to making your experience that less miserable.
Frequently Asked Questions
REFERENCES
American Academy of Dermatology
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DISCLAIMER: The purpose of this site is purely informational in nature. It is not intended to diagnose, treat or cure any medical condition. This information is not a substitute for advice from a medical professional. Please consult your healthcare provider for accurate diagnosis and treatment. The information presented here may be subject to errors and omissions.
SITE LAST UPDATED: October 2026
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