Most people experience absolutely no sensitivity with our products. Only a handful of the thousands of people that used our Home Whitening Kit (with 44% carbamide peroxide gel) have reported any tooth sensitivity or gum irritation. Less than 1% of our customers reported experiencing an allergic type of reaction to our peroxide-based whitening gel. An allergic reaction can be painful and even cause blisters. If this happens to you, discontinue use immediately and, if desired, see your dentist or physician about methods to help the skin heal faster. We recommend applying pure vitamin e oil to the irritated parts of the mouth. People with gum disease might experience irritation because their gum tissues are not healthy. Only use whitening products if your gums and teeth are healthy. People with tiny cracks in their tooth enamel, any stage of dental carries, or very thin or porous enamel might experience tooth sensitivity from peroxide-based whitening gels. If this happens to you, discontinue use and see your dentist if desired.