Hello,
The rash that results from the poison plants is a form of allergic contact dermatitis.
Symptoms include redness and itching of the skin, development of rash and sometimes development of blisters from rash.
Once it begins, the rash will usually clear on its own by 14-21 days. Treatment is directed at controlling the itching. You may take oral antihistaminics like benadryl or zyrtec.Also apply calamine lotion as it has a soothing effect on the skin.