What Causes Severe Sweating?

My husband has always sweat a lot. A little over a year ago, however, it started smelling like vinegar. The smell is so strong that he has to wrap his workout clothes in plastic bags before putting them in the hamper. He also sweats profusely at night, and so I have to wash the bedsheets several times per week due to the vinegar smell. I'm concerned that the smell is an indication of a health problem?