NAC for trichotillomania and skin picking: what the research actually shows

The short answer: NAC (N-acetylcysteine) has two small, well-designed adult trials behind it — one for trichotillomania and one for skin picking disorder — and both found more improvement than placebo.[1][2] A similar trial in children found no benefit.[3] The evidence is promising but thin, it is not a replacement for behavioral therapy, and it is worth talking to a doctor or pharmacist before you start it.

What NAC is, and why researchers tried it

N-acetylcysteine is an amino acid derivative. In the US it is widely sold over the counter as a supplement, and in hospitals it has long been used for entirely different purposes. Researchers became interested in it for body-focused repetitive behaviors because it appears to act on glutamate, a brain chemical involved in reward and habit loops — the trial authors describe it as seeming to restore glutamate levels in a brain region linked to compulsive behavior.[1]

That mechanism is a working theory, not a settled fact. What matters more for you is what happened when people actually took it.

The adult hair pulling trial

The first placebo-controlled study, published in 2009, randomized 50 adults with trichotillomania to NAC (1,200–2,400 mg a day) or a placebo for 12 weeks.[1]

• 56% of people taking NAC were rated “much or very much improved”, compared with 16% on placebo.
• The difference showed up on two separate hair pulling scales.
• Improvement was first noticeable only after about nine weeks — a detail many people miss when they give up after a fortnight.
• No adverse events were reported in the NAC group.

The adult skin picking trial

A 2016 trial in JAMA Psychiatry tested NAC (1,200–3,000 mg a day) against placebo in 66 adults with skin picking disorder, again for 12 weeks.[2]

• On a standard picking-severity scale, the NAC group fell from 18.9 to 11.5; the placebo group fell from 17.9 to 14.1.
• Clinician-rated severity also improved more with NAC than with placebo.

Both results were statistically significant, though the main scale only narrowly so. It is a real signal from a small study, not proof that NAC works for most people who pick.

Two adult trials found NAC beat placebo. One children’s trial found it did not. That is the whole controlled evidence base for the three most-asked questions — and it is smaller than most forum posts suggest.

The children’s trial that did not work

In 2013, researchers ran a similar placebo-controlled trial in 39 children and teenagers aged 8 to 17 with trichotillomania. NAC was added to whatever care they were already receiving. There was no significant difference between NAC and placebo on any measure — 25% of the NAC group responded, compared with 21% on placebo.[3]

The authors’ conclusion is worth repeating for parents: a treatment that helps adults cannot be assumed to help children, and behavioral therapy — which has worked in both age groups — should come first.[3] If you are a parent weighing this up, our guide for parents of children who pull their hair is a better starting point.

How NAC compares with behavioral therapy

A 2020 meta-analysis pooled 24 randomized trials of trichotillomania treatments, involving 857 participants.[4]

• Behavioral therapy with habit reversal training produced the largest benefit of anything studied, and has the strongest evidence base.
• NAC showed a significant benefit over placebo, alongside two prescription medicines — but each of those rests on single trials that, in the authors’ words, would benefit from replication.

A 2022 review of 24 clinical trials, retrospective studies and case reports on NAC across hair pulling, skin picking and nail biting reached a similar view: promising, but based on few trials with small numbers of patients, and larger and longer studies are needed.[5] For nail biting specifically, the evidence is thinner still.

In practical terms, NAC is best understood as something that may make urges easier to manage for some adults — not as the plan itself. The behavioral side, starting with noticing when your hand moves, is where the strongest evidence sits. Our guide to habit reversal training breaks that part down.

If you are thinking about trying it

• Talk to a doctor or pharmacist first, especially if you are pregnant or breastfeeding, have asthma or another long-term condition, take other medicines, or are considering it for a child.
• The trial doses are not a recommendation. They show what was tested (1,200–3,000 mg a day in adults), under supervision, for 12 weeks.
• Give it a fair window. In the hair pulling trial, differences appeared around week nine.[1] Judging it after a few days tells you very little.
• Supplements vary. Products sold as dietary supplements in the US are not approved by the FDA for effectiveness before sale, and quality can differ between brands.
• Keep a simple record. Note roughly how often you pull or pick before you start and every couple of weeks after — otherwise it is very hard to tell whether anything changed.
• Pair it with a behavioral plan. Nothing in these trials suggests NAC works best on its own.

Awaira can help with the record-keeping and the noticing. While you are at a computer or using the phone app, it gives a private, on-device cue when your hand moves toward your face or head, and shows how often that happens over time. It is an awareness tool, not a treatment, and it cannot tell whether a given moment was a pull or a pick.

When to get help

See a clinician if hair pulling or skin picking is causing hair loss, wounds, bleeding, infection, or significant distress — and seek medical advice promptly for signs of infection such as spreading redness, warmth or swelling. A psychiatrist, psychologist or dermatologist who knows BFRBs can help you weigh medication options, including NAC, against your health history. The TLC Foundation for BFRBs keeps a directory of specialists.

Common questions

Does NAC work for trichotillomania?

In the only placebo-controlled adult trial, 56% of people taking N-acetylcysteine (1,200–2,400 mg a day for 12 weeks) were much or very much improved, compared with 16% on placebo. A trial in children and teenagers found no benefit. The evidence is promising for adults but rests on small studies.

Does NAC help skin picking?

A 2016 randomized trial of 66 adults with skin picking disorder found greater reductions in picking severity with N-acetylcysteine (1,200–3,000 mg a day) than with placebo over 12 weeks. It is one small trial, so the result needs replication.

Is NAC effective for children who pull their hair?

A placebo-controlled trial of 39 children and teenagers aged 8 to 17 found no significant difference between NAC and placebo. The authors recommended behavioral therapy before medication for children with trichotillomania.

How long does NAC take to work for hair pulling?

In the adult trichotillomania trial, a significant difference from placebo first appeared after about nine weeks of a 12-week course. Judging it after a few days or weeks is unlikely to be informative.

References

1. Grant JE, Odlaug BL, Kim SW. “N-acetylcysteine, a glutamate modulator, in the treatment of trichotillomania: a double-blind, placebo-controlled study.” Archives of General Psychiatry. 2009;66(7):756–763. PubMed.
2. Grant JE, Chamberlain SR, Redden SA, Leppink EW, Odlaug BL, Kim SW. “N-Acetylcysteine in the Treatment of Excoriation Disorder: A Randomized Clinical Trial.” JAMA Psychiatry. 2016;73(5):490–496. PubMed.
3. Bloch MH, Panza KE, Grant JE, Pittenger C, Leckman JF. “N-Acetylcysteine in the treatment of pediatric trichotillomania: a randomized, double-blind, placebo-controlled add-on trial.” Journal of the American Academy of Child and Adolescent Psychiatry. 2013;52(3):231–240. PMC.
4. Farhat LC, Olfson E, Nasir M, Levine JLS, Li F, Miguel EC, Bloch MH. “Pharmacological and behavioral treatment for trichotillomania: An updated systematic review with meta-analysis.” Depression and Anxiety. 2020;37(8):715–727. PubMed.
5. Lee DK, Lipner SR. “The Potential of N-Acetylcysteine for Treatment of Trichotillomania, Excoriation Disorder, Onychophagia, and Onychotillomania: An Updated Literature Review.” International Journal of Environmental Research and Public Health. 2022;19(11):6370. PMC.