Why does my daughter's skin start to itch one after another when the weather is hot?

What you said is considered to be prickly heat. It is caused by hot weather and poor sweat excretion, and it is often easy to induce skin infection on this basis.

Suggestion:

In order to avoid local scratches, we can consider applying prickly heat powder externally, and at the same time, we can consider decocting watermelon Cui Yi and lotus seeds with water.