If your mother always said: “leaves of three, let it be,” she knew what she was talking about. Direct skin contact with poison ivy is a common cause of allergic contact dermatitis, which manifests as a rash that can be agonizingly itchy and long-lasting.
Some essential facts about poison ivy and poison oak rashes:
• Identifying: Poison ivy is found in forested areas across the much of the United States and Canada. Poison oak is common in southern states. Both plants can be identified by their distinctive sets of three leaves on a stem. Poison ivy leaves have pointy ends, while poison oak has oak-like scalloping at the leaf edges. While more commonly recognized as shrubs, both plants can also grow up trees as vines.
• Poison ivy and oak release a resin called urushiol, and it’s contact with that resin that leads to the rash. Experts say more than half the population of the U.S. and Canada are susceptible to reacting to poison ivy’s urushiol.
• Signs: A poison ivy rash typically occurs within 24 hours, though sometimes it will develop as late as 3 days after exposure. (An old wives’ tale is that the rash appears immediately – not so.) Unfortunately, the symptoms can last for 2 to 3 weeks.
• The rash: in most people, the rash looks like strips of tiny pimple-like blisters and is irritating and uncomfortable. But for some who are highly sensitive to poison ivy, the rash can turn into large, liquid-filled blisters  and is extremely itchy and painful.
• Myths: Contrary to what you may hear or see on the Internet, the rash is not contagious and it does not spread. It just seems as if spreading is occurring, since resin absorbed by the skin may slowly cause increasing blistering.
• Prevention: The key step is to avoid poison ivy/oak whenever possible. Repeated exposures can lead to more severe dermatitis. If going for a nice walk in the woods, cover up: wear long sleeves, pants and sneakers not sandals.
• Treatment: If you think you’ve come in contact with poison ivy or oak, wash your hands with soap and water or use alcohol treated wipes if still in the woods. (This may diminish symptoms, though you’ll likely have some reaction, as the resin gets into the skin.)
Once you start feeling the itch, calamine lotion or hydrocortisone cream can help. A cool water compress may also bring relief. If you’re prone to more serious rashes and blistering, dermatologist Dr. Sandy Skotnicki  says to see your doctor for a prescription-strength hydrocortisone cream.
If you feel nauseated or short of breath after poison ivy exposure, head to the hospital.
• Did you know? The same urushiol resin is also found on mango skins. If you’re susceptible to poison ivy outbreaks, you may also get a rash from mangoes. Peeled mango, however, should not be a problem for those who have contact dermatitis.