Poison Ivy

Poison Ivy

In the U.S., there are five different kinds of poison ivy, poison oak and poison sumac. Different types grow in different parts of the country. All contain the same substance that causes the blistering, itchy rash many of us get upon contact with these plants. It’s called toxicodendrol and it’s a sticky sap in the leaves and branches of the plants. If you’re allergic to the sap (and more than 50 percent of the American population is), the rash breaks out in about 12-72 hours, but only on areas which actually came in direct contact with the sap. By touching areas of your body that came in contact with the sap, you can spread poison ivy to other parts of your body that did not actually come in contact with the plant.

The rash caused by these plants is called rhus dermatitis. It’s usually red, raised and often blistered at the center. Because people usually brush up against the plants in passing, the rash may have a streaky or patchy pattern, unlike stings which are usually single and round. The rash is generally very itchy.

The rash spreads only by spread of the invisible sap on the skin, not by leaking blister fluid from the rash itself. That blister fluid is a product of your own body, and contains no poison ivy sap. The reason the rash often continues to break out in new areas beyond 72 hours is that people unknowingly continue to contact it --- from unwashed clothes (especially shoes and laces), sporting or gardening equipment, pets, etc. Anything that comes in contact with the plant can carry active sap for months!

The sap is so potent, you can pass it from object to object a dozen times just by light contact, and the last object can still cause an intense rash. People leave an invisible "trail" of toxicodendrol where they sit, sleep and touch objects. They end up re-exposing themselves over weeks to come. So don’t worry about your oozing blisters being contagious, just start washing everything you may have touched.

Avoiding contact with these plants is the best way to prevent the rash. The site map included here will help you recognize the different types of poison ivy, oak and sumac in your geographic area. Wear long pants and shoes with socks if you’re going to be outdoors in areas where these plants are likely to grow, such as when going hiking.

If you’ve already come in contact with one of these plants, start washing everything you may have touched. This dramatically reduces the spread of the condition to yourself and others. In fact, if you wash with soap and water within 15 minutes of contact, you may not even get a rash.

Once you have the rash, it can last anywhere from one week to one month. Treatment is directed at the intense itching and at shrinking your rash. Treating the itching is especially important, since scratching can lead to secondary skin infection. Be sure to clip your kids’ fingernails short since they may find it impossible not to scratch.

For Itching:

Antihistamines are available as topical preparations (creams, lotions and sprays) and oral medications. The oral forms are probably more effective but can cause drowsiness. Topical antihistamines are less effective and can cause a rash of their own in some people.

Drying agents like calamine or other lotions are very soothing and speed healing of the rash.

Menthol, benzocaine, and pramoxine are topical anesthetics that numb your itchy rash. They work well but you have to apply them frequently.

Cools soaks in baking soda, commercial oatmeal or colloidal baths for 15 to 30 minutes can relieve itching for several hours at a time. Just add one cup of baking soda or oatmeal to a tub of slightly cool water and soak. If you prefer, you can use a product like Aveeno Oatmeal Bath instead; just follow the directions on the package.

For Rash:

Hydrocortisone creams and sprays reduce the inflammation, swelling and itching of poison ivy rashes. They must be used four times per day for best results.

Lotions containing calamine, zinc acetate and/or alcohol dry the blistered rash quickly and can speed healing.

There are some lotions that have been shown to be effective barriers to toxicodendrol (see Recommended Products section). If applied frequently, they can prevent the typical skin rash. You should still wash after contact with these plants, though, as a further preventive measure.

Burt's Bees Poison Ivy Soap is extremely effective against poison ivy, oak and sumac. This all natural treatment quickly relieves the itching, irritation and inflammation. Other treatments include:

Dermoplast spray (benzocaine 20%, menthol .5%). This quick acting surface anesthetic almost instantly relieves your itching, but is short acting. Works well in combination with oral antihistamines such as Benadryl.

Cortaid (hydrocortisone 1% cream). Over the counter hydrocortisone preparations like this brand work against both the itching and inflammation of allergic-type rashes such as those caused by poisonous plants. They are slow acting.

Caladryl (pramoxine and calamine in suspension). Pramoxine is the topical anti-itching agent in this medication, while the calamine acts a drying agent which tends to promote crusting and flaking of the blistered skin of rhus dermatitis. Many believe this drying effect hastens recovery.

Aveeno Oatmeal Bath (colloidal oatmeal). The exact mode of action of colloidal oatmeal is unknown, but it is proven to relieve itching for up to several hours. It leaves a rather slippery, smooth texture to the skin, in contrast to the dry, rough texture after calamine applications.

Benadryl (pramoxine 25 mg). This brand of antihistamine is particularly effective for uncontrollable itching in the evening and during sleep, when its common side effect of drowsiness combines with its primary anti-itching properties to give much more restful nights.

Far more powerful agents are available by prescription for the rash and itching of poison ivy. Here are some good reasons to seek care from a physician:

Facial or genital involvement. The skin in these areas is easily damaged and scarred, and swelling from rhus dermatitis can be dramatic.

Involvement of large areas of skin. Ten percent of the body’s surface, or about the size of the entire front abdomen, is too large to self-treat.

Signs of infection. These include pain and tenderness, growing redness around the rash, or pus. Clear or slightly yellow transparent fluid is common from poison ivy blisters and is not a sign of infection.

Extreme itching. Itching which disturbs sleep or normal daily activities despite using over the counter treatments should be treated by a physician.

More than poison ivy on our Self Care Home Page