Heat rash? Possibley. I'd have to see a picture.
Yeah, the sun and heat from your body may have caused a skin irritation in those areas. Look into icing and or cooling your wholebody.
Topical creams don't get to the root problem. Your over heated?
Do the links in my post show pictures or can I email them to you? I think the root started when I got selson blue on my skin a few times.