Using an apple cider vinegar soak twice per week over one month may help treat dandruff-related scalp itching, according to TheHealthSite. There is insufficient evidence to support the effectiveness of apple cider vinegar in treating dandruff as of 2015, notes WebMD.
For treating dandruff and scalp itch, apply undiluted apple cider vinegar directly to the scalp, and let it soak for one hour. Use a cotton ball soaked in vinegar for ease of application. Apple cider vinegar may help kill certain bacteria and fungus, explains TheHealthSite.
There are a number of possible underlying causes for dandruff, notes WebMD. One possible cause is an immune reaction to the fungus Malassezia. Apple cider vinegar may have anti-fungal effects.