how to remove white circles under armpit in colored t-shirts?

Question

they are only fine lines, I don't know if they are from sweat or deodorant, they remained after wash the fabric.

Answer 1

You can treat the area with ammonia/water mixture when you remove the shirt. You can leave it on the shirt until you launder as normal

Answer 2

Have you tried washing them?

Washing them will take out the sweat lines but if it's deodorant there's nothing going to get rid of it. I have a few shirts where the pits have hardened and I've tried getting it out but nothing works.