Allergy: Poison Ivy, Oak, and Sumac

Reviewed on 9/19/2022

How to Recognize Poison Ivy, Oak, and Sumac

Pictured are the distinctive leaves of poison ivy, poison oak, and poison sumac. These plants all secrete a chemical that causes itching and rash.
Pictured are the distinctive leaves of poison ivy, poison oak, and poison sumac. These plants all secrete a chemical that causes itching and rash.

More than half the people in the United States are sensitive to poison ivy, poison oak, and poison sumac. If an individual is sensitive, he or she can develop an itchy, blistering rash by coming into contact with these plants.

  • Whether working or just enjoying the outdoors, look out for these plants, and note the differences between each and what each looks like:
    • Poison ivy is generally found east of the Rocky Mountains, growing as vines or shrubs. The leaves can have either smooth or notched edges and are often clustered in groups of three.
    • Poison oak is more commonly found west of the Rockies, usually as a small bush but sometimes as a climbing vine. Its leaves are smooth-edged and cluster in groups of three, five, or seven.
    • Poison sumac is most often found in wet areas of the Southeast. The leaves are generally smooth and oval-shaped, with seven to 13 growing on each stem.
    • The appearance of each of these plants can vary considerably from region to region and with the seasons. Even dead plants in underbrush can transmit the toxic oil to the skin. Identification of these plants can help one avoid them.

Why Does Exposure to Poison Ivy, Oak, and Sumac Cause a Rash?

The rash caused by poison ivy, oak, and sumac is an allergic skin reaction to an oil called urushiol that is inside the plant. This oil is found in all parts of the plant, including the leaves, stems, roots, and berries.

Exposure to the oil occurs through any of the following:

  • Touching any part of the plants
  • Touching clothing or other objects that have contacted the plants
  • Touching pets or other animals that have contacted the plants
  • Exposure to the smoke of burning plants

Poison ivy, oak, and sumac rash themselves are not contagious. However, if oil remains on the skin or on clothing that came in contact with the plants, and the oil comes into further contact with the skin, a rash may result. The rash may appear to "spread" because it can develop over several days, or it's possible the oil was not entirely removed from all surfaces.

Risk factors for developing poison ivy, oak, or sumac rash include being in areas where the plants grow, engaging in outdoor activities, and coming into contact with them.

What Symptoms and Signs Accompany a Poison Ivy, Oak, and Sumac Rash?

  • Exposure to poison ivy, oak, or sumac causes an itching skin rash that usually appears within 24-72 hours.
  • The rash usually starts as small red bumps and later develops blisters of variable size. The rash may crust or ooze. It may look like red, bumpy lines or streaks on the skin.
  • The rash may be found anywhere on the body that has contacted the oil from the plant. It can have any shape or pattern but is often in straight lines or streaks across the skin.
  • Different skin areas can break out at different times, making it seem as if the rash is spreading.
  • Contrary to popular belief, leakage of blister fluid does not spread the rash. It is spread only by additional exposure to the oil, which often lingers on hands, clothing, shoes (which are often overlooked as carriers), or tools.
  • The rash caused by poison ivy, oak, or sumac generally lasts about two to three weeks.
  • While poison ivy, oak, or sumac rash can be persistent, these rashes are not recurrent. The rash does not lie dormant and then reappears in the same spot. If you have a bout of poison ivy, oak, or sumac that seems to recur, it's more likely you encountered the plant again, or oil from the plants may not have been completely removed from all clothing or surfaces. You may also have a bacterial or fungal infection in the same spot that requires treatment.

When Should Someone Seek Medical Care for a Poison Ivy, Oak, or Sumac Rash?

See a healthcare professional for the following conditions:

  • Large areas of rash causing significant discomfort
  • A rash on the mouth, genitals, or around the eyes
  • An area of the rash that becomes infected or drains pus
  • A great deal of swelling

People who are highly sensitive to these plants can get a severe allergic reaction called anaphylaxis.

  • If someone has swelling of the face and throat or difficulty breathing, feels dizzy or faint, or loses consciousness, he or she may be having an anaphylactic reaction.
  • If someone has any of these symptoms, go immediately to a hospital emergency department.
  • Do not attempt to drive; call 911 for emergency medical treatment.
  • While waiting for the ambulance to come, begin self-treatment measures.

What Types of Specialists Treat Poison Ivy, Oak, and Sumac?

Most people will likely see their primary care provider (PCP), such as a family practitioner, internist, or a child's pediatrician, to diagnose and treat poison ivy, oak, or sumac.

  • If you have a severe rash you may see a dermatologist, who specializes in skin disorders.
  • If you have a severe allergic reaction (anaphylaxis), you may see an emergency-medicine specialist in a hospital emergency room.

What Tests to Doctors Use to Diagnose a Poison Ivy, Oak, and Sumac Rash?

A health-care professional can usually make the diagnosis of poison ivy, oak, or sumac by the appearance of the rash alone. He or she will ask some questions about the patient's reaction, symptoms, and medical history.

  • No lab tests or X-rays are needed except under unusual circumstances.

What Are Remedies for Poison Ivy, Oak, and Sumac Rash?

Usually, self-care at home is all that is needed for a reaction to poison ivy, oak, or sumac.

If someone is exposed to any of these plants or their oils, wash thoroughly with soap and water as soon as possible. An alternative is rubbing alcohol, which can dissolve and remove the oils from the skin. If the oil is removed within 10 minutes, it's much less likely a rash will develop.

Symptoms from a mild rash can sometimes be relieved by the following home remedies:

  • Cool compresses with water or milk may help alleviate the itch.
  • Calamine is a nonprescription lotion.
  • Aveeno oatmeal bath is a product that's put in the bath to relieve itching.
  • Burow's solution (Domeboro) can be applied as a compress to blisters to help relieve skin irritation.
  • Oral antihistamines, such as diphenhydramine (Benadryl), may make someone too drowsy to drive a car or operate machinery safely.

Nonprescription corticosteroid (for example, hydrocortisone) creams usually do not help.

Do not use bleach to cleanse rash from poison ivy, oak, or sumac. These areas are open wounds, and bleach is a harsh substance that can damage the skin and slow the healing process.

Do not attempt to treat severe (or anaphylactic, see above) reactions or to "wait it out" at home. Go immediately to the nearest emergency department or preferably, call 911 and take an ambulance. Here are some things to do while waiting for the ambulance:

  • Stay calm.
  • Prevent further exposure to the "poisonous" plant.
  • Take an antihistamine (one to two tablets or capsules of diphenhydramine [Benadryl]) if it's possible to swallow without difficulty.
  • If someone is wheezing or having difficulty breathing, use an inhaled bronchodilator such as albuterol (Proventil) or epinephrine (Primatene Mist) if one is available. These inhaled medications open up (dilate) the airway.
  • If someone is feeling lightheaded or faint, lie down and raise the legs higher than the head to help blood flow to the brain.
  • If someone has been given an epinephrine kit (EpiPen) for a previous allergic reaction, inject the person or oneself as instructed. The kit provides a premeasured dose of epinephrine, a prescription drug that rapidly reverses the most serious symptoms (see Follow-up).
  • If at all possible, someone should be prepared to tell medical personnel what medications the afflicted individual takes and his or her allergy history.

What Is the Medical Treatment for Poison Ivy, Oak, and Sumac Rash?

Like most allergic reactions, treatment is dictated by the severity of the reaction. Reactions that cover a large proportion of the body, make someone uncomfortable enough to disrupt normal activities, or do not get better within a few days may require treatment with prescription medications.

Medications for poison ivy, oak, and sumac rash include:

  • Topical corticosteroid creams (prescription strength): These reduce the immune response and relieve inflammatory symptoms.
  • Oral corticosteroid medication (such as prednisone): These have effects similar to those of the creams but are needed for a more severe or widespread reaction. A course of steroids can run from three days to as long as four weeks.
  • Oral antihistamines -- for itching: The main advantage of prescription antihistamines is that they do not make people sleepy, allowing the individual to carry on his or her normal activities, although some types of second-generation (nonprescription) antihistamines are available over the counter.
  • Antibiotics: These are needed only if the skin becomes infected with bacteria after the initial rash.

Follow-up Care for Poison Ivy, Oak, and Sumac Rash

Someone who is treated by a medical professional should follow his or her recommendations exactly. Use all medications as directed.

  • Return to a doctor if the symptoms do not begin to improve in two weeks.

Are There Ways to Prevent Poison Ivy, Oak, and Sumac Rash?

  • Avoid poison ivy, oak, and sumac plants. Learn what they look like in the area. Be aware their appearance can vary with the seasons.
  • Do not burn the plants. Burning can release allergens into the air, and inhaling particles from burned poison ivy, oak, or sumac plants can cause reactions.
  • Wear proper clothing to protect the skin, such as gloves, long sleeves, and long pants.
  • Bathe pets that may have the oil on their fur. Use soapy water. Wear protective clothing while doing this.
  • Wash any clothing that might contain the plant oil. Unwashed clothes can retain the oil and cause a rash in anyone who wears or handles them.
  • Before going into a potentially infested area, apply nonprescription products such as Ivy Block or Stokoguard, which act as a barrier to the oils.
  • Remember the oil can be transferred from people, pets, or objects. Thoroughly wash anything that may carry the oil.

What Is the Prognosis for Poison Ivy, Oak, and Sumac Rashes?

The prognosis for poison ivy, oak, or sumac rash is generally good. The rash and itching usually get better gradually and go away completely in two to three weeks. Treatment should be continued for at least this long because the rash can come back if medicines are stopped too soon. There may be temporary darkening of the skin when the rash disappears.

  • Complications of poison ivy, oak, or sumac rash include infections, which usually happen as a result of scratching the skin. Redness, pain, and pus surrounding a rash can indicate a skin infection, which a doctor can treat with antibiotics. This is more likely to happen if the rash is scratched so much that the skin is broken.
  • Someone will almost certainly have another reaction if he or she comes in contact with these plants again after a first reaction.
  • In rare instances, complications can result if the airway and lungs are exposed to smoke from burning poison ivy, oak, or sumac plants.

Where Can People Find More Information on Poison Ivy, Oak, and Sumac?

American Academy of Allergy, Asthma & Immunology
555 East Wells Street, Suite 1100
Milwaukee, WI 53202-3823
Patient Information and Physician Referral Line: 800-822-2762

American College of Allergy, Asthma & Immunology
85 West Algonquin Road, Suite 550
Arlington Heights, IL 60005
Email: [email protected]
Phone: 847-427-1200

National Institute of Allergy and Infectious Diseases
Office of Communications and Public Liaison
5601 Fishers Lane, MSC 9806
Bethesda, MD 20892-9806
Toll-Free: 866-284-4107
Local: 301-496-5717
TDD: 800-877-8339 (for hearing impaired)

Learn home remedies for the treatment of poison oak exposure.

Home Remedies for Poison Oak Exposure

Poison oak's resin, called urushiol, can remain active for a very long time. When an allergic reaction occurs after contacting poison oak, the first thing to do is to wash the skin thoroughly with warm soap and water and launder any clothes that may be contaminated with poison oak. This should include towels used to clean the skin. Some soothing remedies such as showering with cool water, applying over-the-counter anti-itching cream, oatmeal baths, or baking-soda mixture may help lessen the discomfort in mild cases. If the allergic reaction is severe, one should contact a physician or go to the emergency room, and some prescription medications including topical and oral steroids may be needed to reduce the swelling and itch.

Reviewed on 9/19/2022
Brown, Sydney Park Brown and Pat Grace. "Identification of Poison Ivy, Poison Oak, Poison Sumac, and Poisonwood." University of Florida IFAS Extension. <>.

Prok, Lori, and Thomas McGovern. "Poison Ivy (Beyond the Basics)." Nov. 25, 2013. <>.