Allergens: Poison Ivy/Poison Oak/Poison Sumac

What are poison ivy, poison oak, and poison sumac?

Poison ivy, poison oak, and poison sumac are native American plants. They may collectively be called poison ivy. These plants cause an allergic reaction in most people who are exposed to them. To be allergic to poison ivy, you must come in contact with the plant once for sensitization to the oils to occur. This means that next time contact with the plant occurs, a reaction may occur. An allergic reaction can’t be spread from one person to another by touching the blisters or from the fluid inside the blisters. But, it can be spread if the plant oils remain on the skin, clothes, or shoes.

What causes the allergic reaction to poison ivy, poison oak, or poison sumac?

The resin in the plants contains an oily substance called urushiol. Urushiol is easily passed from the plants to other objects, including tools and animals. This chemical can remain active for a year or longer. It is important to know that the oils can be passed from clothing, pets, or smoke from a burning plant.

What are the symptoms of an allergic reaction to poison ivy, poison oak, or poison sumac?

The allergic reaction to poison ivy, poison oak, or poison sumac is usually contact dermatitis, which may occur several hours, days, or even weeks after exposure. The dermatitis is characterized by a rash followed by bumps and blisters that itch. Sometimes, swelling occurs in the area of contact. Eventually, the blisters break, ooze, and then crust over.

How is an allergic reaction to poison ivy, poison oak, or poison sumac diagnosed?

Diagnosis is usually based on a medical history and physical exam.

How is an allergic reaction to poison ivy, poison oak, or poison sumac treated?

There is no cure for the reaction once the rash starts. Avoiding the plants is the best treatment. It is very important to learn what the plants look like and to not touch them.

If you have already come in contact with the plants, remove the oils from your skin as soon as possible. Do this by washing with ordinary soap. Repeat the cleaning with the soap 3 times. There are also alcohol-based wipes that help remove the oils. Also wash all clothes and shoes because the oils can remain on them.

For the itching, your health care provider may recommend over-the-counter creams, such as calamine lotion. He or she may also recommend bathing in a baking soda or colloidal oatmeal bath. These can be bought at your local drugstore. Sometimes your health care provider will prescribe a medicine to take by mouth for the itching.

Tell your health care provider if you have a temperature over 100°F (38°C) and the blisters and rash are on your face, in your eyes, near your genitals, or all over your body. After a medical history and physical, your health care provider may prescribe a steroid cream or injection to help with the swelling and itching.

Can an allergic reaction to poison ivy, poison oak, or poison sumac be prevented?

  • Teach all family members what the plants look like.
  • Wear long pants and long sleeves when outside in woods or yard.
  • Wash clothes and shoes immediately after being outside.
  • Do not touch a pet that might have been in a poisonous plant.
  • Wash hands thoroughly.

What are the complications of an allergy to poison ivy, poison oak, or poison sumac?

In some cases, a severe reaction that causes swelling or trouble with breathing or swallowing may occur. If this happens, get treatment right away. This is an emergency.

Living with an allergy to poison ivy, poison oak, or poison sumac

Be sure to follow recommendations for preventing an allergic reaction to these plants by avoiding exposure.

When should I call my health care provider?

While most allergic reactions to poison ivy, poison oak, or poison sumac are easily managed at home, you should call your health care provider right away if:

  • The rash covers all or most of your body
  • You are unable to stop the itching or if it feels like all of your skin is itching
  • You have multiple rashes and/or blisters
  • You get a rash on your face or genital area
  • The itching and discomfort keep you from sleeping
  • You have a fever over 100°F.
  • The rash does not improve after a few days

Call 911 or go to the emergency room if:

  • You have difficulty with breathing or swallowing
  • You have swelling, especially around your eyes

Key points about poison ivy, poison oak, and poison sumac

  • These plants cause an allergic reaction in nearly 85% of the population.
  • An oily substance in the plants called urushiol causes the allergic reaction.
  • The allergic reaction causes a rash followed by bumps and blisters that itch. Eventually, the blisters break, ooze, and then crust over.
  • The best treatment is avoiding contact with poison ivy, poison oak, or poison sumac.
  • There is no cure for the allergic reaction but treatments can minimize the discomfort.

Next steps

Tips to help you get the most from a visit to your health care provider:

  • Before your visit, write down questions you want answered.
  • Bring someone with you to help you ask questions and remember what your provider tells you.
  • At the visit, write down the names of new medicines, treatments, or tests, and any new instructions your provider gives you.
  • If you have a follow-up appointment, write down the date, time, and purpose for that visit.
  • Know how you can contact your provider if you have questions.