Use an Alum Bar to Soothe Razor Burn and Seal Cuts

Next time you cut yourself shaving or need to alleviate razor burn, try an old-fashioned barber trick and reach for an alum bar.

Typically composed of aluminum potassium sulfate (the same stuff you'd find in a deodorant crystal), alum bars are very popular among straight razor enthusiasts and barbers, but can come in handy no matter what type of razor you use. After you're done shaving, just wet the bar and rub it slowly across the sensitive area, pausing on any cuts. It will sting briefly, but soon after the burn should be soothed and the bleeding should be stopped.

Avoid razor burn and make your skin feel great after a shave by using an alum bar | Reddit