Allergies are a common cause of hives since an allergic reaction can trigger the immune system response that results in trapped fluid beneath the skin.An allergic reaction can occur due to something you ingested or were exposed to through the air.hoto Credit pollen image by asb from Fotolia.com. Allergies are a common cause of hives since an allergic reaction can trigger the immune system response that results in trapped fluid beneath the skin. An allergic reaction can occur due to something you ingested or were exposed to through the air.
The median nerve, which runs through the arm and hand, can cause swelling pain and numbness if injured. Ulnar nerve injury Damage to the ulnar nerve causes swelling, pain and numbness in the forearm, hand, and ring and little fingers.
Quick Answer. A possible reason a personâs hands swell during sleeping hours is carpal tunnel syndrome, according to E-Hand.com. The symptoms of carpal tunnel syndrome typically occur while sleeping, because regular use of the hand while awake sends excess fluid outside the carpal tunnel, thus relieving swelling. Continue Reading.