So I'm A 16 Year Old Male And Every Now

so i'm a 16 year old male and every now and then i have these sort a hot flashes and i start to itch all over really bad and it goes away after like 5 minutes of itching and my arms will have these tiny little bumps and it only seems to happen when i start to get active or a get stressful or when im hot and the only way to get relief is rub ice cubes on my neck and back and itch please help me idk what is wrong?