Worry—heat rash?

I tend to exercise a lot.

My skin only reacts during summer, not at all in winter.

It's a mess, messㅠㅠ Is it heat rash or something that keeps turning red?

Come up. It tickles and... I am so nervous.

It wasn't like this before, but maybe it's because my constitution has changed ㅠ

But when I exercise alone, I turn on the air conditioner.

I can't do it... Originally, I didn't use a fan.

Right now, I have the fan on.

But since yesterday, it's been creeping up my arm ㅠ

The first time, I applied ointment and it didn't subside, so I took the emergency-prescribed medication, and at least the itching has lessened.

Is there a good way?