Topic Overview

What are poison ivy, oak, and sumac?

Poison ivy, poison oak, and poison sumac are plants that can cause a skin rash called allergic contact dermatitis when they touch your skin. The red, uncomfortable, and itchy rash often shows up in lines or streaks and is marked by fluid-filled bumps (blisters) or large raised areas (hives). It is the most common skin problem caused by contact with plants (plant dermatitis).

See a picture of poison ivy, oak, and sumac leaves.

What causes a poison ivy, oak, or sumac rash?

The rash is caused by contact with an oil (urushiol) found in poison ivy, oak, or sumac. The oil is present in all parts of the plants, including the leaves, stems, flowers, berries, and roots. Urushiol is an allergen, so the rash is actually an allergic reaction to the oil in these plants. Indirect contact with urushiol can also cause the rash. This may happen when you touch clothing, pet fur, sporting gear, gardening tools, or other objects that have come in contact with one of these plants. But urushiol does not cause a rash on everyone who gets it on his or her skin.

What are the symptoms of the rash?

The usual symptoms of the rash are:

• Itchy skin where the plant touched your skin.
• Red streaks or general redness where the plant brushed against the skin.
• Small bumps or larger raised areas (hives).
• Blisters filled with fluid that may leak out.

The rash usually appears 8 to 48 hours after your contact with the urushiol. But it can occur from 5 hours to 15 days after touching the plant.¹ The rash usually takes more than a week to show up the first time you get urushiol on your skin. But the rash develops much more quickly (within 1 to 2 days) after later contacts. The rash will continue to develop in new areas over several days but only on the parts of your skin that had contact with the urushiol or those parts where the urushiol was spread by touching.

The rash is not contagious. You cannot catch or spread a rash after it appears, even if you touch it or the blister fluid, because the urushiol will already be absorbed or washed off the skin. The rash may seem to be spreading, but either it is still developing from earlier contact or you have touched something that still has urushiol on it.

The more urushiol you come in contact with, the more severe your skin reaction. Severe reactions to smaller amounts of urushiol also may occur in people who are highly sensitive to urushiol. Serious symptoms may include:

• Swelling of the face, mouth, neck, genitals, or eyelids (which may prevent the eyes from opening).
• Widespread, large blisters that ooze large amounts of fluid.

Without treatment, the rash usually lasts about 10 days to 3 weeks. But in people who are very sensitive to urushiol, the rash may take up to 6 weeks to heal.

How is the rash diagnosed?

The rash usually is diagnosed during a physical exam. Your doctor will examine the rash and ask questions to find out when you were exposed to the plant and how long it took the rash to develop. If you are not sure whether you were exposed to a plant, he or she will ask about your outdoor activities, work, and hobbies.

How is the rash treated?

Most poison ivy, oak, or sumac rashes can be treated successfully at home. Initial treatment consists of washing the area with water immediately after contact with the plants. To relieve symptoms, use wet compresses and take cool baths. Nonprescription antihistamines and calamine lotion also may help relieve symptoms. Moderate or severe cases of the rash may require treatment by a doctor, who may prescribe corticosteroid pills, creams, ointments, or shots (injections).

How can I prevent the rash from poison ivy, oak, and sumac?

The best way to prevent the rash is to learn to identify and avoid the plants. When you cannot avoid contact with the plants, heavy clothing (long pants, long-sleeved shirt, and vinyl gloves) and barrier creams or lotions may help protect you.

Frequently Asked Questions

Cause

Contact with poison ivy, oak, or sumac plants can cause a rash (allergic contact dermatitis). The rash is caused by contact with the oil (urushiol) in these plants. Urushiol is an allergen, so the rash is actually an allergic reaction to the oil in poison ivy, oak, or sumac.

• The leaves, stems, vines, twigs, berries, and roots of these three plants contain urushiol, even after they have died.
• Urushiol is a colorless, odorless, sticky oil that is easily spread before a rash develops.
• The rash can also occur after indirect contact with this oil. This may happen when you touch clothing, pet fur, sporting gear, gardening tools, or other objects that have come in contact with one of these plants.

No one is born allergic to any of these plants. You become allergic to them through contact with them (or with other plants). After you have been in contact with one of the plants one or more times, your body's immune system may recognize urushiol as an allergen and you may have an allergic reaction. You may be more or less sensitive than other people to the plants. A more sensitive person will react after contact with only a small amount of urushiol and have a more severe reaction.

Symptoms

The most common symptoms of the rash (allergic contact dermatitis) from poison ivy, oak, or sumac are:

• Itching.
• Red streaks or general redness where the plant brushed against the skin.
• Small bumps or larger raised areas (hives).
• Blisters filled with fluid that may leak out. In rare cases, some people develop blood-filled blisters that can turn black and become shiny dark spots.

The rash may have several stages, and its severity can also vary. It usually appears 8 to 48 hours after you have contact with the plant oil (urushiol). But it may occur up to 15 days after the contact.¹ The rash will continue to develop in new areas over several days but only on the parts of the skin that first had contact with the plant oil or those parts where the oil was spread by touching. Blister fluid cannot spread the rash. Areas where the skin is thick, such as the soles of the feet and the palms of the hands, are less sensitive to the oil.

People who are highly allergic to the urushiol in these plants can develop more serious symptoms that may require medical treatment. Serious symptoms may include:

• Swelling of the face, mouth, neck, genitals, or eyelids (which may prevent the eyes from opening).
• Widespread, large blisters that ooze large amounts of fluid.

Other conditions with similar symptoms

Other kinds of plant rashes can look like a poison ivy, oak, or sumac rash. These include rashes caused by:

• Other plants, such as the ginkgo tree, which contain urushiol or a similar oil.
• Irritant plants, such as stinging nettle. These rashes are not caused by allergic reactions.
• Phytophotodermatitis, which may happen when you touch certain plants and then go into the sun.

Skin conditions that may look like the rash from poison ivy, oak, or sumac include:

• Scabies, an itchy skin condition caused by mites.
• Shingles (herpes zoster), a viral skin infection.
• Impetigo, a bacterial infection of the skin.

Insect bites, exposure to nickel and other metals, and exposure to chemicals found in fabrics, lotions, or laundry detergent may also result in a similar skin rash.

What Happens

Contact with poison ivy, oak, or sumac can cause a rash (allergic contact dermatitis). The rash is caused by contact with the oil (urushiol) in these plants. Urushiol is an allergen, so the rash is actually an allergic reaction to the oil in these plants.

Normally, the immune system protects the body from viruses and bacteria by producing antibodies to fight them. In an allergic reaction, the immune system overreacts and starts fighting essentially harmless substances as though these substances were trying to attack the body. This overreaction causes problems that affect the skin, nose, lungs, digestive organs, and blood vessels. In the case of contact with poison ivy, oak, or sumac, it results in a rash.

You are not allergic to these plants until contact with urushiol triggers a reaction. The contact with urushiol can either be direct or indirect, such as through clothes, tools, or other objects.

Most poison ivy, oak, and sumac rashes develop within 8 to 48 hours after touching urushiol, but they can take as long as 15 days to form.^{2, 1} The rash usually takes more than a week to show up the first time you get urushiol on your skin. But the rash develops much more quickly (in 1 to 2 days) after later contacts. The rash usually lasts 10 days to 3 weeks, but more severe cases can last up to 6 weeks.¹ After the rash heals, there are usually no permanent scars on the skin.

The rash is not contagious. You cannot catch or spread the rash after it appears, even if you touch it or the blister fluid, because the urushiol will already be absorbed into or washed off the skin. Sometimes people mistakenly believe that the rash is spreading because it appears later on different parts of the body. But the rash only appears where urushiol has come in contact with the skin. So either the rash is still developing from earlier contact or you have touched something that still has urushiol on it.

How sensitive you are to poison ivy, oak, or sumac and the severity of your reaction depend primarily on your age and on the extent of the first contact or first few contacts with the plant. Other influences include physical activity and immune system function. Some studies show that how allergic you are to the plants may be inherited.¹

Complications

Complications from a poison ivy, oak, or sumac rash usually do not occur in healthy people.

• The rash can occur all over the body (generalized eruption) in highly allergic people.
• Excessive scratching of the rash may discolor the skin or cause a bacterial infection.
• The rash may come back or get worse if treatment ends too soon or if the medicine used is not strong enough.
• In rare cases, kidney problems (nephrotic syndrome) can occur. This can happen in any severe allergic reaction and is not specific to poison ivy, oak, or sumac.

What Increases Your Risk

People in certain jobs or with outdoor hobbies have an increased risk for contact with poison ivy, oak, or sumac and the resulting rash (allergic contact dermatitis). These people include:

• Landscapers.
• Forest firefighters and forestry workers.
• Electrical linemen.
• Those who install fences.
• Maintenance workers in parks, gardens, and nurseries.
• Hikers, campers, rafters, kayakers, and fishermen.

Your risk of reacting to poison ivy, oak, or sumac and the severity of your allergic reaction depend mainly on your age and on the extent of the first contact or first few contacts with the plant. Other influences include physical activity and immune system function.³ Some studies show that how allergic you are to the plants may be inherited.¹

When To Call a Doctor

Call a doctor if:

• The rash (allergic contact dermatitis) from poison ivy, oak, or sumac causes great discomfort that is not relieved by home treatment (for instance, you apply calamine lotion to the rash, but itching continues to make it difficult to sleep).
• The rash shows signs of infection, such as pain, swelling, or warmth around the affected area.
• The rash covers a very large area of the body.
• Home treatment causes the rash to get worse or to come back after nearly disappearing.
• Rashes occur frequently, and you are not sure what is causing them. (The rashes may be caused by another kind of plant.)
• Your mouth is swollen or you think the rash has spread to your mouth.
• The rash has spread to your face, particularly around an eye.
• You have a rash and a weakened immune system.

Call 911 if you are having a hard time breathing.

Watchful Waiting

Watchful waiting is a wait-and-see approach. If the rash is not severe, watchful waiting may be appropriate. Home treatment may be used to relieve symptoms. Dark spots may develop, but this is not serious.

Watchful waiting is not appropriate if the rash develops over your entire body, becomes infected, or reappears or gets worse after using medicine. See your doctor.

Who To See

You may not need to see a doctor for the rash. But if you want to find the cause of the rash or if you want to treat an uncomfortable, severe, or infected rash, you may choose to see:

• A family medicine doctor.
• An internist.
• A pediatrician.
• A dermatologist.
• A physician assistant.
• A nurse practitioner.

To prepare for your appointment, see the topic Making the Most of Your Appointment.

Exams and Tests

A rash (allergic contact dermatitis) from poison ivy, oak, or sumac plants usually is diagnosed through a physical exam and questions about your outdoor activities. Your doctor will examine the rash to decide which kind of plant caused it and ask about:

• The length of time between possible exposure and development of the rash.
• The length of time you were out in the sun.
• What you were doing when the exposure may have occurred (hiking, for example).
• Other rashes you have had.
• Your job and your hobbies.

Diagnosis is harder when there are no clues that you have been in contact with the plant. Sometimes indirect contact with the plant oil (urushiol) causes the rash. Urushiol that is on clothing or other objects may spread to your skin months after initial contact. If a bacterial infection is suspected, your doctor may take a sample of blister fluid for a culture.

If your primary care doctor is not sure of the cause, you may need to see a dermatologist for a direct patch skin test. In this test, small amounts of allergens are placed on the skin and covered with a bandage for several days. The patch is then removed and the skin is examined for reactions.

Treatment Overview

The rash (allergic contact dermatitis) from poison ivy, oak, or sumac generally is mild and can be treated at home. Home treatment for the rash usually helps relieve symptoms but does not speed up healing of the rash.

• If you know you had contact with one of these plants, immediately wash areas of the skin that may have touched the plant. Sometimes the rash can be completely avoided by washing the affected areas with plenty of water within 10 or 15 minutes of contact. You could also try using a product (such as Tecnu or Zanfel) that is designed to remove the oil from your skin.
• To relieve itching and help dry blisters, apply wet compresses or soak the area in cool water. Antihistamine pills or calamine lotion may help relieve symptoms.
• If you have a moderate to severe rash, you may need to see your doctor. He or she may prescribe corticosteroid pills. These medicines may help improve or clear up the rash more quickly. Prescription corticosteroid creams, ointments, gels, or shots may also be used.

A frequent complication of the rash is infection. If this occurs, your doctor will probably prescribe an antibiotic cream that you spread on the affected skin if the infection is small. Otherwise, you may need antibiotic pills or a shot. To prevent infection, try not to scratch the rash. Cut your fingernails short to minimize the possibility of opening the skin and spreading bacteria.

Regardless of what type of treatment is used after a rash develops, the length of time it lasts will vary from person to person.

Prevention

Only the oil (urushiol) from poison ivy, oak, or sumac plants can cause a rash (allergic contact dermatitis). The best way to avoid contact with urushiol and getting a rash is to avoid the plants.

• Learn to recognize these plants, especially those near where you live. The plants may look different depending on the season and the area where they are growing. A county agricultural extension service may be able to help you identify the plants in your area. See a picture of poison ivy, oak, and sumac leaves.
• While their appearance changes with the seasons, the plants usually contain the same amount of urushiol year-round, even in the winter when they only appear as bare sticks. Black areas on the plants may help you identify them in the winter (urushiol turns black when exposed to air). Living, dormant, and dead plants all contain urushiol, although dead leaves do not contain a lot of it.
• You may also try to remove the plants when appropriate. Never handle these plants without vinyl gloves (urushiol can penetrate rubber).
• When you cannot avoid being near poison ivy, heavy clothing (long pants, long sleeves, enclosed footwear) may help prevent the oil from touching your skin. Clothing or any other object that has touched the plant must be handled carefully and washed thoroughly.
• If you are often in areas where poison ivy, oak, or sumac grows, you may want to get a product (such as Tecnu or Zanfel) that is designed to remove the plant oil (urushiol) from your skin.
• Barrier creams and lotions can be used to prevent urushiol from contacting the skin or to reduce the severity of a reaction. These creams vary in their potency and are not always effective.

If you suspect that your skin has touched poison ivy, oak, or sumac, rinse the area with water immediately (within 10 to 15 minutes) to help prevent a reaction. Most of the oil is absorbed into the skin within 30 minutes.¹ Clothing should also be thoroughly washed right away. Contaminated surfaces should be cleaned with rubbing alcohol.

Home Treatment

The rash (allergic contact dermatitis) from poison ivy, oak, or sumac generally is mild and can be treated at home. Home treatment for the rash usually helps relieve symptoms rather than speeding up the time it takes the rash to heal.

• If you know you had contact with one of the plants, immediately wash areas of the skin that may have touched the plant. Sometimes the rash can be completely avoided by washing the affected areas with plenty of water within 10 or 15 minutes of contact. Most of the oil is absorbed into the skin in the first 30 minutes.¹ Clothing should also be thoroughly washed right away. Contaminated surfaces should be cleaned with rubbing alcohol.
• To relieve itching and help blisters dry out, apply wet compresses or soak the area in cool water. Antihistamine pills or calamine lotion may help relieve symptoms.
• To prevent infection, try not to scratch the rash. Also, cut your fingernails short to minimize the possibility of opening the skin and spreading bacteria.

Medications

Antihistamine pills are used to relieve the symptoms of the rash from poison ivy, oak, or sumac. Prescription medicines, such as corticosteroids, may be used for severe rashes. Medicines are also used to make the rash less severe.

Medication Choices

• Antihistamine pills can help relieve itching and dry blisters. Examples include Benadryl (diphenhydramine), which is an over-the-counter medicine, and Vistaril (hydroxyzine), which you get by prescription.
• Corticosteroids may be used to treat a moderate or severe rash. Corticosteroids may be given as pills, products that are spread on the skin (creams, ointments, gets), or shots.
• Barrier creams and lotions help prevent the plant oil (urushiol) from coming in contact with the skin or reduce the severity of a reaction. These creams vary in their potency and are not always effective.

You may be able to use a product that dissolves urushiol, such as Tecnu or Zanfel. These products are used to wash the oil off your skin or other objects. They may reduce the severity of a reaction or prevent one.

The most common complication of poison ivy, oak, or sumac rash is a secondary infection, usually caused by scratching. When this occurs, your doctor will probably prescribe a type of topical antibiotic cream if the infection is in a small area. Otherwise, you may need systemic antibiotics, given as prescription pills or shots.

What To Think About

The following medicines should not be used for poison ivy, oak, or sumac rash, because they can cause allergy problems of their own:

• Antihistamines applied to the skin, such as diphenhydramine (found in Benadryl cream, spray, or gel).
• Anesthetics applied to the skin containing benzocaine (such as Lanacane).
• Antibiotics containing neomycin (such as Neosporin or Poly-Pred).

Surgery

There are no surgical treatments for a poison ivy, oak, or sumac rash.

Other Treatment

Creating tolerance and reducing sensitivity

Some cultures, including certain Native American cultures, have used homeopathic treatment for poison ivy, oak, or sumac as a means of preventing the rash (allergic contact dermatitis). Stories of successful prevention of rash through eating the leaves are common, but research studies have failed to reproduce these results without the people involved in the studies developing mild to serious side effects.

Other Places To Get Help

Organizations

Related Information

• Blisters
• Rash, Age 12 and Older

References

Citations

1. Gladman AC (2006). Toxicodendron dermatitis: Poison ivy, oak, and sumac. Wilderness and Environmental Medicine, 17(2): 120–128.
2. Anderson BE, Marks JG Jr (2007). Plant-induced dermatitis. In PS Auerbach, ed., Wilderness Medicine, 5th ed., pp. 1262–1286. Philadelphia: Mosby Elsevier.
3. Tanner T (2000). Rhus (toxicodendron) dermatitis. Primary Care, 27(2): 493–501.

Other Works Consulted

• Guin JD (2001). Treatment of toxicodendron dermatitis (poison ivy and poison oak). Skin Therapy Letter, 6(7): 3–5.

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