A little swelling in the palm of the hand may be caused by skin allergies, blood clots in the veins of the head and arm, and local soft tissue injuries. 1. skin allergy: this phenomenon is mainly seen in patients with special sensitivity, if the patient is allergic to a certain food or drug, after contact or taking, the palm of the hand may be swollen. 2. Venous thrombosis in the head and arms: Accompanied by venous thrombosis in the upper limbs, it will lead to obstruction of venous blood return, and a large amount of blood will accumulate in the blood vessels around the palms of the hands, which will lead to obvious swelling in the palms of the hands, accompanied by pressure pain. If the blood vessels are seriously blocked, patients will have localized skin tension blisters. 3. Local soft tissue injury: accidental fall during strenuous exercise, resulting in the palm of the hand touching the ground, can lead to local soft tissue injury, with obvious swelling. In addition to the above factors, there may be other reasons, it is recommended to go to the hospital as soon as possible to check by the doctor to clarify the cause of the disease, give targeted treatment.