Apple Cider Vinegar for Hair: What Happens If You Leave It on Overnight?
Apple cider vinegar (ACV) is a popular DIY hair rinse, but claims that leaving it on overnight will dramatically transform your hair are not supported by scientific evidence. In fact, leaving ACV on your scalp for many hours may increase the risk of irritation, especially if it is undiluted.
Potential Benefits of Apple Cider Vinegar
When properly diluted and used as a short rinse, ACV may:
1. Reduce Product Buildup
It can help remove residue left by styling products or hard water, making hair feel cleaner.
2. Add Shine
By smoothing the outer layer of the hair (the cuticle), a diluted ACV rinse may make hair appear shinier.
3. Reduce Frizz
Smoother hair cuticles can make hair look less frizzy and easier to manage.
4. Help With Mild Scalp Buildup
Some people find that a diluted ACV rinse helps remove excess oil or flakes, although it is not a proven treatment for dandruff or scalp conditions.
Why You Shouldn’t Leave It on Overnight
Leaving ACV on your hair or scalp overnight can:
- Irritate the scalp
- Cause dryness
- Damage sensitive skin if it’s too concentrated
- Increase discomfort if you have eczema, psoriasis, or broken skin
Undiluted vinegar is acidic enough to cause skin irritation or even mild chemical burns in some people.
A Safer Way to Use It
If you want to try an ACV rinse:
- Mix 1–2 tablespoons of apple cider vinegar with 1 cup (240 mL) of water.
- Apply it after shampooing.
- Leave it on for 1–5 minutes.
- Rinse thoroughly with cool or lukewarm water.
Use it no more than once a week at first to see how your hair and scalp respond.
Who Should Avoid It?
Avoid using ACV if you have:
- Cuts or sores on your scalp
- Very sensitive skin
- Active eczema or psoriasis on the scalp
- A known allergy to vinegar
The Bottom Line
A diluted apple cider vinegar rinse may make some people’s hair feel cleaner, smoother, or shinier, but leaving it on overnight is unlikely to provide extra benefits and may irritate your scalp or dry out your hair. If you try ACV, dilute it well, use it briefly, and discontinue use if irritation occurs.
