If you touch or even get near poison ivy, you can develop an itchy, blistering rash within 72 hours. Though the rash usually goes away after a short time, some people can have serious reactions that require a trip to the doctor. To help manage a poison ivy rash, the American Academy of Dermatology offers these suggestions: wash anything that may have come in contact with the oil; avoid scratching, which can trigger an infection; take lukewarm soapy baths to ease itching; apply calamine lotion or hydrocortisone cream to the rash; and take an antihistamine if recommended by your physician. American Academy of Dermatology, September 2018