Mommies my 3yr old been going to the pool these past 2 weekdays. &’ yesterday he was complaining…

Mommies my 3yr old been going to the pool these past 2 weekdays. &’ yesterday he was complaining that he was real itchy. But when I scratched I didn’t notice anything on his skin.

Well today I look at his arms &’ they look like this. He has it all over his entire body!!

If I apply Calamine or hydrocortisone cream will it help?? What do y’all think??