It's probably not this but I just recently saw a programs on TV called "Monsters inside me" and there were a couple of stories that sound a bit like what you are describing, where a rash-like thing comes out, it itched like crazy, the lady put some antibiotic ointment on it, within a few days it went away, but some time later it resurfaced. It ended up being some kind of parasite/worm that somehow found a way to get in the body and it is potentially deadly if not treated right away. I suggest going to a dermatologist or family doctor. Good luck.
Hi
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Itchy localized rash can be due to allergic dermatitis, eczema, scabies, contact dermatitis, shingles, psoriasis, or fungal infection like Tinea. It could also be a food allergy. So look back and see if there is some food that causes the rash or something else-maybe a bush or portion of playground or something he plays with just few hours prior to the rash. Consult a skin specialist to find the cause. Take care!
Please write me back and tell me what the bumps look like if they are small and little tiny bumps with red or if they are something else?