As warmer weather kicks into full gear, people are pulling out the lawnmowers, dusting off the hiking boots and looking forward to Saturday picnics by the lake. But while everyone might enjoy spending time outdoors, no one enjoys a nasty bout of poison ivy.

Reactions to poison ivy, or its kin poison oak and poison sumac, are the most common allergy in the U.S. The potent irritant that makes poison ivy such a well-known foe is urushoil, and only a pin-head sized amount could trigger itching in roughly 500 people.

This poisonous sap is found throughout the plant, from roots to fruit, and is released when the plant is bruised or broken. The plant is surprisingly fragile, and is easily damaged by wind, wild animals and insects. Once the plant is damaged, all it takes is brushing up against it to transfer the sap from plant to skin.

“It is responsible for varying degrees of irritation from skin inflammation to blistering,” says Wake County Extension Agent Angelo Randaci. “You don’t even have to touch it. You can get it from smoke if it is being burned. It is said that even 100-year-old leaves can cause irritation.”

Once the toxin has hit skin, it works quickly, binding to skin proteins. Within 36 hours, an itchy rash and watery blisters appear. This uncomfortable reaction often lasts up to 15 days.

“The best precaution and defense is recognizing it and avoiding it,” Randaci says. “Many times though, the recognition occurs too late. After coming in contact with it, the first reaction seems to be to touch it or scratch it. The best advice is to avoid touching the exposed area no matter how badly it itches until you can wash it.”

Randaci recommends a well-known natural remedy for coping with a poison ivy reaction—jewel weed, which is found in two different varieties, with a yellow flower (Impatiens pallida) or with an orange flower (Impatiens capensis).

“The great thing about jewel weed is that it often grows right next to poison ivy and is fairly common along roadsides,” Randaci says. “It is a well-known folk remedy for poison ivy and has no reported side-effects.”

The juice of the jewel weed can be extracted from the stems or leaves and applied to the affected area. The juice can also be frozen by shredding the leaves and roots and placing them in boiling water for 15-30 minutes and then freezing in ice cube trays. Randaci also recommends applying baking soda, cooked oatmeal or vinegar to the area for relief from itching.

Many people claim to have immunity to poison ivy, but there is little validity to that statement. While some might not have had the misfortune of a reaction to poison ivy, many health professionals say that true immunity is rare.

“People’s bodies respond differently to exposure to poison ivy. You may get into it once and not experience any effects, but can get it the next time,” Randaci says. “Sometimes people who have been seemingly immune to the exposure will have a bout that will make up for all of the times when they were in it before and didn’t get it.”