That’s definitely hives and not eczema. I would do an eliminate and see what’s causing it. Sounds crazy but If she’s sweating a lot some people do react to their own sweat it’s rare but can happen
@onlyluvremains, has anything been different this year? Laundry soap, fabric soap, lotion, body wash, shampoo, conditioner, hair products, foods she’s never had. I deal with allergies with my kids so I’m well aware of hives and having to get to the root of the problem lol