Contact Dermatitis Topic Guide
Poison Ivy, Oak, and Sumac Poison ivy, poison oak, and poison sumac can causes an allergic reaction when someone comes in contact with the plant. This oil is called urushiol. The resulting rash appears one to three days after contact and may crust or ooze. Home remedies for the rash include applying cool compresses and calamine lotion, soaking in an Aveeno bath, and taking oral antihistamines.