Apple cider vinegar can help treat scalp and hair conditions like dandruff, itching, thinning hair, and baldness. It does this by killing bottle bacillus, a germ that causes these issues by clogging hair follicles and reducing oil production. To use it, apply apple cider vinegar to the scalp before shampooing to restore pH balance and treat dandruff. It can also be mixed with oils and applied to moisturize dry hair or stimulate regrowth when combined with cayenne powder.