Make sure it's really poison ivy first. My hubby gets poison ivy easily, but one time he had a rash on his back and side. He didn't get it checked out, but I really think it was shingles. According to a website it said shingles can be activated by stress and that you shouldn't eat nuts and some other food I forgot. He stopped eating nuts, and my MIL made fresh peppermint oil from the peppermint in our flower beds. They put the peppermint oil everyday to help ease the ich and I'd put hydrogen peroxide on it at night to help it heal faster. It finally went away, but it takes 3-4 weeks to go away.
As for poison ivy. It can be poison ivy, because you can accidently transfer it from your arms to any location on your body just by itching the poison ivy spot,then forgeting and touching another part of your body. Always try to wash the area that touches poison ivy with COLD water and soap ASAP. I finally got it after all these years. Never had it before. I noticed that the calamine lotion hubby uses, just doesn't look like it works and it's not really 100% calamine like use used to be able to get years ago. I decided to try witchhazel. To my surprise the witchhazel worked and I got rid of my poison ivy a lot faster than he did. I tired the witchhazel, because that is what I use on my pets. I use a cottonball moistened with witchazel to get rid of the ear mites my dog had one time....alternated with baby oil...just make sure it's a damp cottonball and not wet...You don't want any liquid going down the dog's ears....I used witchazel when my cat had acne and it worked great.