.Treat immediately. Once you come into contact with the poison sumac, you need to remove the urushiol resin on you. Put the affected skin in running water and wash your clothes using soap and water. You need to remove any traces of the urushiol resin to make sure that it does not affect your skin any further than the initial contact. You can do this within 15 to 20 minutes of contact with the poison sumac. The less skin that comes into contact with the urushiol resin the better for you. Wait for rashes to appear. Even if you know which parts of your body came into contact with the poison sumac, you have to wait a couple of days before the rashes come out so you can apply the lotion. You can’t put the lotion on in anticipation of the rash as it will do no good without any rashes to soothe. Usually it takes up to 3 days for the rashes to show up. Then, and only then, can you apply the calamine lotion. Apply calamine lotion. As soon as the rash appears, slather on the lotion. Make sure that you cover all the areas that the rash covers. Do not skimp out! Put on the lotion as thick as you can because the lotion will harden and form a protective layer over the blisters. Allow the affected area to breathe. Keeping the rash area suffocated under a bandage will only make the recovery longer. It’s best that you keep the affected area exposed to air. Don’t wear restrictive clothing while recovering from the poison sumac. Don’t scratch! Scratching the blisters will only expose your rashes to infection and could prolong recovery. It’ll feel better if you scratch the itchy blisters but this is counter-productive to the healing process. If the itching becomes too unbearable, you can make yourself an oatmeal bath using colloidal oats in lukewarm water. Soak yourself in it for half an hour. If you follow the steps above, you should make a full recovery in 2 to 3 weeks.