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Signs and symptoms of a poison ivy rash include:

• Redness
• Itching
• Swelling
• Blisters

Often, the rash looks like a straight line because of the way the plant brushes against the skin. But if you come into contact with a piece of clothing or pet fur that has urushiol on it, the rash may be more spread out.

The reaction usually develops 12 to 48 hours after exposure and can last up to eight weeks. The severity of the rash is dependent on the amount of urushiol that gets on your skin.

In severe cases, new areas of rash may break out several days or more after initial exposure. This may seem like the rash is spreading. But it's more likely due to the rate at which your skin absorbed the urushiol.

Your skin must come in direct contact with the plant's oil to be affected. Blister fluid from scratching doesn't spread the rash, but germs under your fingernails can cause a secondary bacterial infection.

When to see a doctor
See your doctor if any of the following occur:

• The reaction is severe or widespread.
• The rash affects sensitive areas of your body, such as your eyes, mouth or genitals.
• Blisters are oozing pus.
• You develop a fever greater than 100 F (37.8 C).
• The rash doesn't get better within a few weeks.

©1998-2012 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
Read this article on Mayoclinic.com.

Poison ivy, poison oak and poison sumac can all cause contact dermatitis and the resulting itchy rash.

• Poison ivy is an extremely common weed-like plant that may grow as a bush, plant or thick, tree-climbing vine. The leaves typically grow three leaflets to a stem. Some leaves have smooth edges, while others have a jagged, tooth-like appearance. In the fall, the leaves may turn yellow, orange or red. Poison ivy can produce small, greenish flowers and green or off-white berries.
• Poison oak can grow as a low plant or bush, and its leaves resemble oak leaves. Like poison ivy, poison oak typically grows three leaflets to a stem. Poison oak may have yellow-white berries.
• Poison sumac may be a bush or a small tree. It has two rows of leaflets on each stem and a leaflet at the tip.

The irritating substance is the same for each plant, an oily resin called urushiol. When your skin touches the leaves of the plant, it may absorb some of the urushiol made by the plant. Even a small amount of urushiol can cause a reaction. Urushiol is very sticky and doesn't dry, so it easily attaches to your skin, clothing, tools, equipment or pet's fur.

You can get a poison ivy reaction from:

• Direct touch. If you directly touch the leaves, stem, roots or berries of the plant, shrub or vine, you may have a reaction.
• Urushiol remaining on your skin. You may develop a poison ivy rash after unknowingly rubbing the urushiol onto other areas of your skin. For example, if you walk through some poison ivy then later touch your shoes, you may get some urushiol on your hands, which you may then transfer to your face by touching or rubbing.
• Urushiol on objects. If you touch urushiol left on an item, such as clothing or firewood, you may have a reaction. Although animals usually aren't affected by urushiol, if it's on your pet's fur and you touch your pet, you may develop a poison ivy rash. Urushiol can remain allergenic for years, especially if kept in a dry environment. So if you put away a contaminated jacket without washing it and take it out a year later, the oil on the jacket may still cause a reaction.
• Inhaling smoke from burning poison ivy, oak or sumac plants. Even the smoke from burned poison ivy, poison oak and poison sumac contains the oil and can irritate or injure your eyes or nasal passages.

A poison ivy rash itself isn't contagious. Blister fluid doesn't contain urushiol and won't spread the rash. In addition, you can't get poison ivy from another person unless you've had contact with urushiol that's still on that person or on his or her clothing.

©1998-2012 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
Read this article on Mayoclinic.com.

Scratching a poison ivy rash with dirty fingernails may cause a secondary bacterial infection. This might cause pus to start oozing from the blisters. See your doctor if this happens. Treatment for a secondary infection generally includes antibiotics.

©1998-2012 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
Read this article on Mayoclinic.com.

You probably won't need medical treatment for a poison ivy rash, unless the rash persists for more than a few weeks or you think you may have a bacterial infection too. If you're concerned you'll probably first see your primary care physician. However, you may be referred to a doctor who specializes in skin disorders (dermatologist).

Because appointments can be brief, and there's often a lot of ground to cover, it's a good idea to arrive well prepared. Here's some information to help you get ready for your appointment, and what to expect from your doctor.

What you can do

• Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
• Write down key personal information, including recent vacations or time spent outdoors, especially if you've been hiking, gardening or landscaping.
• Make a list of all medications, vitamins and supplements that you take, including information on your usual dose.
• Write down questions to ask your doctor.

Your time with your doctor is limited, so preparing a list of questions can help you make the most of your time together. For a poison ivy rash, some basic questions to ask your doctor include:

• What's the most likely cause of my symptoms?
• Are there other possible causes for my symptoms?
• Do I need any tests?
• How long will this rash last?
• Is it OK to scratch?
• Will scratching spread the rash?
• Will popping the blisters spread the rash?
• What treatments are available, and which do you recommend?
• What types of side effects can I expect from treatment?
• What can I do to help control the itching?
• How can I prevent this in the future?
• Are there any brochures or other printed material that I can take home with me? What Web sites do you recommend visiting?

What to expect from your doctor
Your doctor is likely to ask you a number of questions, such as:

• When did you begin experiencing symptoms?
• Have you had a similar rash in the past?
• Have you spent time outdoors recently?
• What treatment steps have you already tried?

What you can do in the meantime
A poison ivy rash will eventually go away on its own. But, the itching can be difficult to deal with. Here are some steps you can take to help control the itching:

• Apply an over-the-counter corticosteroid cream for the first few days.
• Apply calamine lotion.
• Take oral antihistamines, such as diphenhydramine (Benadryl, others), which may also help you sleep better.
• Soak in a cool-water bath containing a colloidal oatmeal product (Aveeno) or baking soda.
• Place cool, wet compresses on the affected area for 15 to 30 minutes several times a day.

©1998-2012 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
Read this article on Mayoclinic.com.

You generally won't need to see your doctor for a poison ivy rash. However, if you do visit your doctor, he or she will be able to diagnose your rash by looking at it. No further testing is needed.

©1998-2012 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
Read this article on Mayoclinic.com.

Poison ivy treatments are usually limited to self-care methods, and the rash typically goes away on its own within two to four weeks. In the meantime, you can use poison ivy remedies, such as oatmeal baths and cool compresses, as well as over-the-counter anti-itch medications to relieve your signs and symptoms.

If the rash is widespread or results in a large number of blisters, your doctor may prescribe an oral corticosteroid, such as prednisone, for poison ivy treatment. If a bacterial infection has developed at the rash site, your doctor will likely give you a prescription for an oral antibiotic.

©1998-2012 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
Read this article on Mayoclinic.com.

Once a rash has broken out, the following poison ivy remedies may help to soothe itching and swelling:

• Over-the-counter low-potency corticosteroid creams, such as hydrocortisone, applied two to four times a day
• Calamine lotion
• Oral antihistamines, such as diphenhydramine (Benadryl, others), which may also help you sleep better
• Cool-water tub soaks with over-the-counter colloidal oatmeal (Aveeno) or baking soda
• Cool, wet compresses for 15 to 30 minutes several times a day

©1998-2012 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
Read this article on Mayoclinic.com.

In addition to self-care measures, such as taking an oatmeal bath, some people may seek out alternative therapies to help control symptoms associated with poison ivy, oak and sumac. Some treatments that have been tried include:

• Jewelweed. This plant was used as a Native American treatment for poison ivy. However, a randomized, controlled study found that it isn't effective.
• Bovine cartilage cream (5 percent concentration). A study done in the 1970s found that when applied daily, this cream helps to clear a poison ivy rash within one to two weeks.
• Deodorant containing aluminum chlorohydrate. Spray this deodorant on your skin and clothing before heading outdoors, and you may help prevent urushiol from irritating your skin. Of course, it's still a good idea to wash your skin and clothes as soon as you can if you think you've brushed up against poison ivy.

©1998-2012 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
Read this article on Mayoclinic.com.

The advice "Leaves of three, let them be" is familiar to many people, with good reason. It's a reminder to stay away from plants that feature three leaflets to a stem, such as poison ivy, because avoiding contact is the best way to prevent an allergic reaction.

These suggestions may help you avoid a rash from these irritating plants:

• Identify poison ivy, poison oak and poison sumac. Learn what the plants and leaves look like and where they're commonly found so that you can avoid them.
• Take precautions outdoors. When hiking or engaging in other activities that might expose you to poison ivy, try to stay on cleared pathways. If camping, make sure you pitch your tent in an area free of poisonous plants. Keep pets from running through wooded areas so that urushiol doesn't accidentally stick to their fur, which you then may touch. If you think your pet may have run through poison ivy, oak or sumac, put on some long rubber gloves and give your pet a bath to remove any residual urushiol.
• Remove poison ivy. In your backyard, you can use an herbicide to get rid of poison ivy or use heavy gloves to carefully pull it out of the ground. Note that even dead plants can cause a reaction. Afterward, remove and wash your gloves and hands thoroughly. Don't burn poison ivy or related plants because the urushiol can be carried by the smoke and cause irritation or injury.

• Clean anything that may be contaminated. Wearing long pants, socks, shoes and gloves will help protect your skin, but be sure to wash your clothing promptly with detergent — in a washing machine, if possible — if you think you've come into contact with poison ivy. Handle contaminated clothes carefully so that you don't transfer the urushiol to furniture, rugs or appliances.

  In addition, wash any other contaminated items, such as outdoor gear, garden tools, jewelry, shoes and even shoelaces, as soon as possible. If you must wait to wash any contaminated items, seal them up in a plastic bag or container to avoid contamination of other items. Dry cleaning also will get rid of urushiol, but be sure to let your dry cleaner know that the item may have been exposed to poison ivy.

• Wash your skin with soap and water. Gently washing off the harmful resin from your skin, using any type of soak, within five to 10 minutes after exposure may help avert a reaction. After an hour or so, however, the urushiol has usually penetrated the skin and washing won't necessarily prevent a reaction, but it may help reduce its severity. Be sure to wash under your fingernails too.
• Apply a barrier cream. Appy an over-the-counter barrier skin cream containing bentoquatam (Ivy Block) to protect your skin. Bentoquatam absorbs urushiol and prevents or lessens your skin's reaction to the oil.

©1998-2012 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
Read this article on Mayoclinic.com.