Hello, Thank you for trusting HealthcareMagic for your health concern The rash of shingles and contact dermatitis caused by poison ivy can be difficult to differentiate. Both are characterised by redness, itching and blistering. The important differentiating factor is that shingles affect nerve roots and will appear only in the dermatome support by the particular nerve. Poison ivy can spread to different and wider areas of the body. Shingles usually does not cross the body midline, whereas poison ivy can. Since in your case larger and wider areas of the body is affected, poison ivy is more likely. Hope this answers your questions Please address further questions here Regards Dr.Lekshmi