Liquid nitrogen is used mainly for treatment of Solar Keratoses (actinic keratosis / sun spots). However, it is also often used to treat viral warts. After application, you may experience a burning sensation for about 10 minutes. By the next day, a blister often forms. This blister darkens to form a black scab. Within about 5 days, the scab loosens and falls off. It is best to leave the scab on until it falls off naturally as it acts as a natural dressing over the treated area. Liquid nitrogen may leave a white scar behind, but this safer than having a potential skin cancer. Occasionally, more than one treatment may be required.