Cura-Heat works with the use of penetrating heat action, which targets the pain at the source from the outside and works its way in. The activated carbon, iron and water work together to create heat which provides 12 hours worth of pain relief. Cura-Heat Period Pain Heat Patches use heat therapy to relieve your muscle soreness and menstrual cramps. When the pad is activated, it heats up in just a few short minutes, sending relieving heat through your muscles, easing muscle stiffness and soreness while easing your pain. Cura-Heat Period Pain Heat Patches can help to relieve your pain for up to 12 hours.