Reason for sweating too easily?

my husband sweats way too fast we can be driving to the stop and he has to turn the a/c up high because he is sweating. he carrys a rag around because he sweats a lot and easily normally you can see it running down his face. he doesn't do out side work, i dont know if diabetics have this sign (he could be due to this?) he does smoke cigs but i have no idea nor does he of why he sweats so easily. please advice would be helpful