Subject: Why do some people 'sweat' more than others?

My friend seems to have a sweat problem.  She perspires quite a 
lot when it is hot & it make her clothes wet under her arm 
pits.  When that drys it causes dis-colouration of her clothes 
(yellow stains).  She hasn't successfully found a good brand of 
deodorant to stop this problem & replacing clothes & people 
noticing sweat marks is upsetting her.  Her sweat doesn't smell 
even when dried.  She showers at least once a day.   She has had 
the problem since 18, she is now 25. She is 5 for 2 inches, 7 & 
a half stone and in good health.  Diet isn't as good as it 
should be.
Thank you very much for your time and help. 

Re: Why do some people 'sweat' more than others?