Razor burn can be treated with a gentle astringent, such as witch hazel, and a thin application of over-the-counter cortisone cream. Aloe vera gel can also be used to soothe and cool the skin.
Razor burn is a pink to red rash that occurs after shaving. There may also be bumps visible on the skin. When the rash appears, rinse the skin with cool water. Then, take a cotton ball or pad soaked with witch hazel, and apply it to the irritated skin. Aloe vera can also be used. If the rash is severe, apply a thin covering of cortisone cream to the skin. Use cortisone cream sparingly, as it can cause stretch marks and thinning of the skin, even at low doses. While the skin heals, try to take a break from shaving.
It's better to prevent razor burn where possible. First, moisten the skin with warm water, and use a thick shaving cream or gel for sensitive skin. Second, shave in the direction of hair growth, not against it. And don't press too hard; that only further irritates the skin. Rinse the blade with each pass for more even cutting. Finally, moisturize the skin with a hypoallergenic, fragrance-free lotion.