Poison Ivy Dermatitis
They do not have the reaction to urushiol that humans have.
You already know it can be carried in on a dogs coats, on camping equipment, lawn tools and even your own clothing and shoes. It will survive for long peroids of time, will still break you out during the dead of winter when it is dried up. Make sure you know what poison ivy, oak and sumac look like. I have seen people trip all over poison sumac shrubs, litterally step all up in them to avoid a strip of virginia creeper vine.
The natural remedy for poison ivy/oak/sumac is jewel weed (Impatiens capensis) aka common jewelweed or touch-me-not.