WUKA Heat Patches - Brand New Sealed - 12 Hour Period Pain Relief - Self Heating Brand new sealed WUKA Heat Patches (1pcs). Self-heating patches providing up to 12 hours of soothing relief for period pain and cramps. Quick acting - starts heating within 30 seconds. Sticks to underwear, not skin. Contains natural ingredients: iron powder, activated charcoal, motherwort and mugwort extract.