Poison Ivy
Poison ivy is a common native plant/vine that produces an substance that causes a rash when it comes into contact with skin. Most people get a mild to moderate reaction after contact, but some people can have a severe reaction to poison ivy, and others may not react at all. There is more poison ivy around these days because poison ivy loves the increased CO2 levels in the air.
Spend some time learning how to identify poison ivy so you can avoid it!