It happens for various reasons. For example, if there is high blood pressure in the hand, if there is anemia , if there is any problem in the nerve , there is tension in the tendon or ligament of the hand. Do this exercise forty times a day and thrice a day. Eat foods rich in calcium and potassium every day. Like eggs , milk , bananas and apples. Eat more water. Do not carry heavy things in your hands.