Burn it..
But as that answer has already been given by people(the only 100% cure)
Check what it says on the packaging, if it says it's wrinkle free, it's a blend.
If it doesn't shrink, can be ironed, it'd be pure cotton product.
If the place where you say, its hot enough that you sweat, take a pinch of talcum powder on your thumb. Rub it over fabric. If the feel stays the same, as it does using just a wet finger, it's cotton. If you feel that it feels coarser with the sweat finger than finger dipped with water, it's a blend.(too hard to interpret for people with no prior
knowledge)
