I use gold bond corn starch based powder all over body for sweating. i tend to inhale a lot when applying it. is this harmful?

Not unless allergy: not unless you are allergic to it i am not sure the long term effect of inhaling any material is safe you need to be more selective when using tha powder and keep it away from your lungs you are too young to keep exposing yourself and your lungs to anything good luck

Powder can harm lung: A substance foreign to the lung can set up an inflammatory response in the lung which can lead to a short term reaction like swelling and / or spasm in the lung or a long term effect where the structure of the lung tissue becomes so thick the effected part of the lung can no longer get oxygen into the body and bad gases out properly. If this area is too wide, one can become a lung cripple.