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MD Mama

Things you might not know about poison ivy

Adapted from the MD Mama blog on Boston.com.

Just the other day, a mother told me that her husband took the kids for a hike — through a whole bunch of poison ivy.

“So far, no rashes,” she said. “I keep checking.”

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And she does need to keep checking, because the rash can take a week or longer to appear (usually with a first exposure), something this mom knew but lots of people don’t. There are lots of other things that people don’t know about poison ivy. Here are a few:

There are different kinds of poison ivy and it can look different at different times of year. The adage “leaves of three, let them be” simply won’t keep you away from everything that can give you a poison ivy rash. The Poison Ivy, Oak and Sumac Information Center has pictures.

You don’t have to touch it to get the rash. The toxin, urushiol, in the leaves escapes when leaves are broken or bruised. It can get on things, like gloves, garden tools, and clothing. It can even get into the air if leaves are mowed. This is why . . .

You can get the rash from people or pets. When you touch (or pet) them, you can get a rash if they have the toxin on them. You can’t get the rash from someone’s rash — it’s not contagious that way.

The best thing to do is to wash immediately. Take off any contaminated clothing, and wash with mild soap and water as soon as you can. That’s the best thing to get at least some of the urushiol off your skin. Clean under nails, too.

There are various rashes you can get from poison ivy. You can get bumps, scales, and various size bubbles and blisters. Often they will be in a line or streak, showing where the plant touched the skin. It’s usually red (although it can have black spots when the toxin stays on the skin and oxidizes) and itches like crazy.

Treating the itch is all you usually need to do. Oatmeal baths or cool compresses can make a difference. Anti-itch preparations that have menthol or phenol, like calamine, can also help, as can Burow’s solution or Domeboro. Interestingly, antihistamines like Benadryl don’t help all that much because of the way urushiol causes itching. Steroid creams may help if used early, but once there are bubbles or blisters, they don’t help much.

Sometimes you need to take steroids, and if you do, you need to go off them slowly. In severe cases, taking steroids by mouth is needed. But if you take them for just a few days, like we often prescribe for asthma, the rash can come back. So the recommendation is to lower the dose bit by bit over two or three weeks.

If you’re ever not sure about a rash, your doctor is your best resource. You should also call your doctor if a rash you think is poison ivy is on the face or genitals, is getting worse, gets very swollen or has pus coming out of it. And you should call if there is fever or the person seems ill.

Read this blog at Boston.com/MDMama.

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