Deep Heat Plaster is used to relieve muscle and joint pain and provides localized heat to help relax muscles and reduce spasms. It is used for muscle strains, sprains, back and neck pain, and rheumatism. It also helps improve blood flow to the affected area, which contributes to accelerating healing. The plaster is applied to dry skin at the site of pain and left for several hours according to the instructions. Deep Heat should not be used on wounds or irritated skin, and it should be avoided for long periods or repeatedly without consulting a doctor.