Automatic Moist Heat Pack. Penetrating moist heat for deep, temporary pain relief. Arthritic and rheumatic pain is often temporarily relieved with the use of moist heat. The increased blood flow can relieve inflamed joints and maintain flexibility. Moist heat can also temporarily relieve back pain caused by over-exertion, stress and strain. Moist heat relaxes muscle spasms. This pack produces it’s own moisture using humidity in the air.