I am 25 yrs 5'1'' , 45 kg.

I have got heat rashes on arm pit , breast area, neck,back and groin area.As per my local doctors suggestion I started applying cloben-g and tablet nuforce 150(two tablets for two weeks).First time i am getting rashes.I am living in chennai (climate is hot here).I sweat a lot.

could you be kind enough to explain me on the reasons for heat rashes and prevention for heat rash. How could I prevent this from occurring again.