Poison Ivy Allergy

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The majority of Americans are allergic to poison ivy. The allergy culprit is urushiol, a plant oil that triggers skin symptoms known as allergic contact dermatitis. It’s also found in poison oak and poison sumac. Poison ivy and poison oak both grow as vines or shrubs while poison sumac is a tree.

poison ivy

The rash that forms from contact with urushiol usually doesn’t spread. It stays in the area of the skin that was in contact with the plant. If your rash does spread, it may be a separate condition that requires medical attention.

You can experience an allergic reaction to poison ivy by touching it directly, touching contaminated objects, or inhaling smoke from the burning plant. Most rashes develop within 24 hours, but sometimes they can appear days later.

If you’ve never been exposed to the plant, symptoms can be delayed much longer. The immune system doesn’t immediately register poison ivy as a potential threat. Those that spend a lot of time outdoors are the most at risk of developing a poison ivy allergy.

Poison Ivy Allergy Symptoms

  • Red streaks or patches
  • Intense itching
  • Rash or hives
  • Swelling of the skin
  • Blisters
  • Inflammation and a burning sensation
  • Difficulty breathing if you’ve inhaled smoke from the burning plant

These symptoms are usually not severe, and disappear in 2-3 weeks. However, some blisters can become infected by scratching. Symptoms of an infected blister include:

  • Tenderness and redness around the skin
  • Excess fluid in the blister
  • Fever or chills (this could indicate cellulitis, a serious bacterial skin infection)

Diagnosing A Poison Ivy Allergy

An allergist can tell just by looking at your skin whether you’ve been exposed to poison ivy. Since up to 85% of the American population is allergic to poison ivy, an allergy test isn’t necessary. Many people have never come in contact with the plant and manage to avoid it throughout their entire lives.

You should never attempt to bring on allergic symptoms by touching poison ivy to diagnose yourself. There is a very high chance that you are allergic to it.

Poison Ivy Allergy Treatment

Symptoms will resolve on their own within 2-3 weeks. Try not to scratch the rash, as it can cause an infection. To soothe the itching, use calamine lotion or hydrocortisone cream. These can be purchased over the counter at your local pharmacy. A cool water compress may also bring relief to your itching.

If you’ve developed an infection by scratching your blisters, you will need an oral antibiotic prescribed by a doctor. The allergists at NY Allergy & Sinus Centers can treat your infection as well as any other symptoms you experience.

Frequently Asked Questions

Where Is Poison Ivy Found?

Poison ivy is found throughout most of North America, except for desert areas, Hawaii, and Alaska. It can grow in open, wooded, and damp areas.

How Do I Know if I’m Allergic to Poison Ivy?

If you’re allergic to poison ivy, you will develop an irritating rash after touching the plant. The rash will often look like a straight line.

Is the Rash from Poison Ivy an Allergic Reaction?

The rash from poison ivy is considered an allergic reaction. There are some individuals that are resistant to the plant and do not react to urushiol.


If your poison ivy rash has lasted more than 3 weeks, seek medical attention. The rash may have developed into a more serious condition. It’s best to avoid this plant whenever possible. NY Allergy & Sinus Centers can provide you with tips or more information on how to identify poison plants. Call (212) 686-4448 to book your appointment with a board certified allergist.