<s>[INST] My son who is 7 yrs old has a rash and welps on his calf muscles only. It started about 8 hours ago. His calves are hot to touch and swollen. He has no other symptoms. We've not changed any detergents nor has he taken any meds lately. What could be wrong? [/INST] Hello,This could be insect bites or allergy to something he has come in contact with. If he develops fever, nausea or vomiting he should see a doctor. Use cool compresses on the rash and give him some childrens antihistamine.Regards </s>