Poison Ivy Dermatitis

Poison Ivy Dermatitis

Prevention and treatment of exposure to the dreaded “leaves of three”

By Angela Toms, M.D.

In our part of the world, after the mud dries up and the temperature rises, we are elated to see the sun shine and the grass turn green. To treat our cabin fever, we venture outside into the fields and woods. Our children might be hiking at camp, retrieving an overthrown ball from the edge of the field, wrestling with buddies by the edge of the stream, or helping us clean up brush around the house, when days later they start to itch.

What is it?

While there are lots of summer rashes that itch, one of the most common summer rashes is poison ivy dermatitis. This very itchy and red rash is caused by an allergic reaction after contact with plants like poison ivy, poison oak, and poison sumac, members of the Toxicodendrum genus which appropriately means “poisonous tree.” These plants contain an allergic compound called uroshiol. When this colorless oil touches the skin it causes a reaction in about 85 percent of people. Any contact with the roots, leaves, stem (even a vine with no leaves), or sap of this plant can cause the rash.

Spot it before it “spots” you

Many know the saying, “Leaves of three, let them be.” This rhyme is helpful because the plant’s leaves grow in clusters of three. Being able to visually recognize poison ivy is the first step in avoiding it. This can get tricky, though, because the same plant may look different depending on the season and geographical region. In the east, the plant is vine; in the west, it’s a shrub. Young poison ivy leaves are green, then turn red or brown and eventually fall off. It tends to grow at elevations below 4000 feet, so lying in the grass at the top of Mount Moosilauke is probably okay. Already know you’re at risk of a severe reaction? Ask your doctor about a product called bentoquatam (Ivy Block).

Soap and water — on the double!

So, what if you don’t notice the shiny leaves of three and end up in contact with poison ivy? As soon as possible, remove any clothing around the exposed area and then gently wash the skin and fingernails with soap and water. There’s no need to scrub. A study once showed that washing 10 minutes after exposure removed 50 percent of the uroshiol, after 30 minutes removed 10 percent, and after an hour removed none of it. Still, washing helps reduce the severity of the reaction even 2 hours after exposure. Remember to wash all clothing, tools, and pets, too!

What to expect

The rash will be very itchy and red in areas where oil made contact with skin. Bumps and blisters may form (often in lines or streaks if the plant brushed the skin) and may develop over time rather than all at once — usually within 14 days after exposure. Poison ivy dermatitis usually lasts 1 to 3 weeks and most of the time does not require a visit to the doctor. Sometimes, after a week or so, the rash will spread to areas that definitely did not touch the oil. When this happens, it’s called a generalized dermatitis, or an “id” reaction.” Note that touching the rash or the blister fluid cannot spread poison ivy, as long as all of the uroshiol oil is washed off initially.

In some situations, you should call your doctor. These include: if the rash is severe, very swollen or covers a large part of the body; the face or genitals are involved; you’re not sure the rash really is poison ivy dermatitis; the rash appears infected — is oozing pus, is very red and hot, and/or is accompanied by a fever; or the rash does not get better after 2 to 3 weeks.

Knowledge is the Best Prevention

Since we want our families to have lots of fun outdoors without suffering the itchy rash of poison ivy dermatitis, take some time to learn what poison ivy, poison sumac, and poison oak look like, and then teach your kids how to avoid these plants. My family enjoys reading Fancy Nancy: Poison Ivy Expert, by Jane O’Conner. Fancy Nancy helps remind us that even experts can get poison ivy dermatitis, but we’d much rather avoid the rather itchy and unpleasant experience if possible!

Parent Tips
  • Try not to scratch!
  • Take oatmeal baths and place cool, wet washcloths or towels on the skin.
  • Use calamine lotion.
  • Use products that have aluminum acetate in them (like Burrow’s Solution or Domeboro) if the rash is wet and weepy.
  • Oral antihistamines (like Benadryl) are commonly used for itching, but may not be that helpful.
  • Over-the-counter topical steroids may make a difference before blisters develop and help with itching after blisters form, but are not as helpful as their prescription-strength counterparts.

Angela Toms, M.D., is a family physician at White River Family Practice. She lives on a small farm with her husband and four children as well as cows, pigs, sheep, chickens and dogs.

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