My 2 y/o son gets a red, not swollen, blotchy edged patch on one leg. I would blame it on heat but it is only one leg (mostly outside bottom half of leg and slight on thigh). I would blame allergies but we can t nail down anything that he comes in contact with only on that part of the leg or any environment that causes it. It does seem to happen when the weather gets hot (we live in Florida so that is often). It does seem to be radiating some heat of its own.
Hi, Thanks for writing to Chat Doctor.For your description he seems to be suffering from Fungal Rash. Your description fits in for Ringworm. Does it scratch a lot? Also cut and file his nails, else he will spread it to other parts by scratching. You may use POTASSIUM PERMANGANATE powder in bath water till it turns a bit pink, and use CLOTRIMAZOLE cream over those rash. If no improvement consult a pediatrician.  Hope you find this helpful. Thanks. If you have any more queries I am happy to answer them. Else, please rate this answer and close the discussion