Sweat allergy? Options

[xoxoxx]

hello.

lately, or actually, since last summer, I've started to get extremely itchy when I sweat.

my sweat would make my body itchy, and parts of my body would turn red, like I get whipped or something.

this also happened when I swam in a pool, after coming out, I starting itching a lot. there were other people in the pool who didn't itch.

swimming in the ocean almost killed me, my body turned so red and itchy.

and showers used to make my body itchy too, after I dried off.

is it like, some lack of vitamins, or something.

this never happened when I was little, and I swam a lot.

please help.