Definition: Hyperhidrosis is a medical condition in which a person sweats excessively and unpredictably. People with hyperhidrosis may sweat even when the temperature is cool or when they are at rest. 
Hyperhidrosis is defined as sweating that disrupts your normal activities. To be diagnosed with hyperhidrosis the patient must have episodes that occur at least once a week without an obvious reason. This is excessive sweating that can soak through clothing, and is often found on the feet, underarms, head or face. 
Sweating helps the body stay cool, and is perfectly natural. However, excessive sweating occurs without common natural triggers of exercise, warm temperatures, or nervousness and can be socially uncomfortable. Patients with hyperhidrosis appear to have overactive sweat glands.
When excessive sweating affects the hands, feet, and armpits, it’s called primary or focal hyperhidrosis. Primary hyperhidrosis is estimated at 2.8% of the population, yet less than 40% of patients with this condition seek medical advice.  Hyperhidrosis affects men and women equally, and most commonly occurs among people aged 25–64. About 30–50% have another family member afflicted, implying a genetic predisposition to the condition. 
If abnormal sweating occurs as a result of another medical condition, it is called secondary hyperhidrosis.  The sweating may be all over the body, or it may be in one area. There are several conditions that cause secondary hyperhidrosis. These include, but are not limited to:
Diagnosis of Hyperhidrosis
Tests that can be performed by your doctor to test for hyperhidrosis include:
Starch-iodine test. An iodine solution is applied to the sweaty area. After it dries, starch is sprinkled on the area. The starch-iodine combination turns a dark blue color wherever there is excess sweat. 
Thermoregulatory Sweat Test. The findings from the thermoregulatory sweat test help your doctor accurately make a diagnosis and define the severity of the hyperhidrosis. During this test, a moisture-sensitive indicator powder is applied to your skin. The powder changes color from yellow-green to dark purple in areas where excessive sweating occurs. This test is performed first at room temperature and then at high heat and humidity in a sweat cabinet that causes sweating over the entire body. 
Paper test. Special paper is placed on the affected area to absorb the sweat, and then weighed. The heavier it weights the more sweat has accumulated. 
At Home Remedies
In addition to antiperspirants, the following suggestions may help you reduce sweating and the associated body odor:
1.. Haider, A; Solish N (January 2005). “Focal hyperhidrosis: diagnosis and management”. Canadian Medical Association Journal172 (1): 69–75.