Some people sweat too little (a condition called hypohidrosis). Diminished sweating is usually limited to a specific area of the body. It can be caused by a skin injury (such as from trauma, radiation, infection [such as leprosy], or inflammation) or by a connective tissue disease (such as scleroderma, systemic lupus erythematosus, or Sjögren's syndrome) that wastes away the sweat glands. Diminished sweating also may be caused by drugs, especially those that have anticholinergic effects (see Aging and Drugs: Anticholinergic: What Does It Mean?). Nerve damage caused by diabetes (diabetic neuropathy) can also cause diminished sweating, as can a variety of syndromes existing at or before birth. Sometimes, people who have very severe heatstroke stop sweating.
A doctor makes the diagnosis by observing the person. If there is diminished sweating over a large portion of the body, the person may overheat, and cooling measures (such as air-conditioning and wearing wet garments) are the best treatment.
Resource: Merck Manual Home Edition