7yo has rashes on both upper arms. Raised red bumps. Itchy. Doesn't look like hives. Allergic reaction?

Skin rash. The differential is very large. Could be sun exposure. Could be contact dermatitis. I would follow up with your family physician or dermatologist and give a more detailed rendering. When did it happen? Was the child taking any medication at the time? Any travel history? Use of new detergents or change in clothes? Have a great day.