Leaving apple cider vinegar on your hair overnight can feel like a daring experiment, but its effects depend heavily on how it’s used. Diluted properly, the acetic acid can help rebalance scalp pH, dissolve product buildup, and create a smoother cuticle, leaving hair looking shinier and feeling lighter. Its mild antimicrobial action may calm dandruff and reduce itchiness for some people, especially when flakes are linked to yeast or irritation rather than severe skin conditions.

However, undiluted or overly frequent use can backfire—causing dryness, breakage, or a stinging, sensitized scalp. The safest approach is mixing one part ACV with three to five parts water, applying it mainly to the scalp after shampooing, and rinsing after a few minutes rather than sleeping in it. Listening to your hair and skin is crucial; if you feel burning, tightness, or unusual shedding, stop immediately. Used with care, ACV can be a helpful ritual, not a reckless gamble.