What Causes Itching Sensation All Over Body After Exercising?

All of my life I have been a pretty physically active person. The past two years, not so much. When I started taking walks, my whole body would itch all over for days and I would have to stop my walking routine. Finally, I adjusted to walking. Now, I have tried to run and lift weights and the itching was so bad it felt like I was wearing astro turf. There is nothing on my skin, but it does appear mottled ...lightly pink all over and my face gets a slight rash. I itch for about a week and lost sleep due to it. The sensation feels like when your tiny body hairs shift under your clothing, but its amplified by about 1000...like a tickling. I also start to get acne on my face, shoulders and chest. I have tried Benadryl, fungal creams, fluconazole, garlic pills, apple cider vinegar bathes and ingestion, and cannot seem to figure out why I am knocked on my butt so bad when exerting myself. Other than these symptoms, I am healthy, 36 yr. old female w/no health problem history and not on any meds. Help!