A Safe & Effective Method for all Hot & Cold Therapeutic Treatments. To heat: place eye mask in the microwave for a maximum of 15 seconds. Due to microwave variations, time may require adjustment. Reheat at 5 seconds intervals as needed. Warning: do not over-heat, heat on stove top or in oven as it will damage product! To chill: store eye mask in the refrigerator or place in the freezer for 30 minutes or until desired coolness is achieved.