Part 3 in a series on avoiding, preventing, and treating poison ivy rash.

FACT: Scratching a poison ivy rash WILL NOT cause it to spread.

Busting the Myth: Poison ivy rashes often seem to spread beyond the site of initial reaction—a fact that many people attribute to scratching the itch, or to spreading the fluid contained in the small to large blisters that form in allergic response. The reality is that reaction time varies by location (thicker skin takes longer to react), and by the amount of exposure to poison ivy’s rash-causing urushiol oil. As a result, a rash caused by the same exposure will often appear over the course of many hours or even days.

Another reason rashes may appear to spread is from re-exposure to urushiol oil. Given that urushiol will rub off and adhere to virtually everything (clothing, garden tools and gloves, pets, shoes, etc.), and that it’s a stable, long-lived substance (up to several years), it’s possible to unknowingly contact the rashy stuff again well after the initial exposure. This can cause a new rash to develop, which—if it follows on the heels of an earlier rash—can give the impression that the earlier rash is spreading.

Nonetheless, scratching the itch is not recommended. It may provide (very) temporary short-term relief, but can slow the healing process and increase the risk of infection.

FACT:  A poison ivy rash is NOT contagious.

Busting the Myth: Say dad or mom is out working in the yard, comes into contact with poison ivy, and develops a rash. A few days later, somebody else in the house develops a rash–somebody who had no direct exposure to poison ivy but lots of direct contact with the rash-bearing parent. Clearly it’s contagious, right? Wrong.

A poison ivy rash will only develop if you are exposed to urushiol oil. If somebody else in the house develops a rash, it’s because he or she has come into contact with the stuff. Perhaps dad or mom sat down on the couch still wearing contaminated clothing, or the family dog was wallowing in the stuff and spread it all over, or some other equally common scenario.

FACT: Your sensitivity to poison ivy CAN CHANGE over time.

Busting the Myth: A few lucky people (an estimated 10 to 30 percent of the population) do not react to urushiol oil. And many of those believe that they’re safe and protected for life. Wrong. You can develop sensitivity at any point, and it is likely that multiple exposures to poison ivy increase the likelihood for developing an allergic reaction.

I’m a case in point. For the first 30 years of my life, I never reacted to the stuff. But lo and behold, after a day spent ripping out poison ivy (with gardening gloves and a long-sleeve shirt, mind you), I developed a (mild) rash around my wrist. These days, I now definitely react to the stuff, albeit mildly.

Alternatively, people with a stronger reaction may find that it diminishes—or gets worse—over time. The upshot remains the same. No matter whether you’re sensitive or not, avoid, avoid, avoid if at all possible.