Low Doses of Common Antibiotic Can Treat Rare Chronic Hair Loss

Small amounts of a common antibiotic and anti-inflammatory drug can curb symptoms where a misplaced immune reaction (e.g., autoimmunity) can cause permanent hair loss, a new study shows. This regimen may also come with fewer side effects than higher doses of the medication.

Led by researchers at NYU Langone Health, the study explored lymphocytic scarring alopecia, a rare skin condition in which the body’s immune cells damage hair follicles, leading to hair loss and scarring. Physicians typically treat this chronic disorder with relatively high doses of the antibiotic doxycycline, often for prolonged periods of time. However, the drug can trigger nausea, vomiting, and rashes and may discourage patients from continuing to take it, the study authors say. As a result, the team set out to determine whether lower doses could work instead.

The findings in 241 men and women treated for several forms of lymphocytic scarring alopecia revealed that lower doses (usually 20 milligrams taken twice daily) and higher doses (as much as 100 milligrams taken twice daily) of doxycycline were equally effective. Specifically, the researchers found no significant difference between the two groups on evaluations of scalp inflammation, patients’ perception of the severity of their hair loss, and clinical measurements of hair density, hair-shaft diameter, and hairline recession.

In addition, while 23 percent of those on the high-dose regimen experienced common negative side effects of doxycycline, only 12 percent of those taking smaller doses of the drug did so. Another key finding was that while 25 percent of the high-dose group stopped taking doxycycline altogether due to gastrointestinal issues, only 16 percent of the low-dose group stopped treatment due to this side effect.

“Our findings suggest that physicians can prescribe lower doses of doxycycline to patients struggling with lymphocytic scarring alopecia without compromising the efficacy and anti-inflammatory benefit of the therapy,” said study co-lead author Carli Needle, BA.

Needle, a medical student at NYU Grossman School of Medicine, adds that besides warding off unpleasant side effects, lower doses of the drug may also safeguard gut health. Doxycycline, she notes, is known to harm the helpful bacteria that live in the digestive tract and bolster the body’s defenses against disease-causing microbes. However, past studies have shown that drug doses below 40 milligrams are less risky for beneficial microbes.

The new study is the first to directly compare the efficacy of different-size doses of doxycycline to treat lymphocytic scarring alopecia, says Needle.

A report on the findings published March 18 in the Journal of the American Academy of Dermatology.

For the study, the research team collected data from electronic medical records of patients with scarring alopecia treated at NYU Langone Health between 2009 and 2023. Of these, about 27 percent had been prescribed low doses of doxycycline and nearly 73 percent were on traditional high-dose regimens. Next, the team ran a statistical analysis to compare the two groups. The researchers discounted from their analysis any effects of other medications that commonly accompany this treatment, such as the hair-growth drug minoxidil.

According to the authors, a further advantage of reducing doxycycline doses is that experts have linked the drug to the rise of dangerous bacterial populations that can survive antibiotic treatments. Clinicians worldwide are now seeking to combat such antibiotic resistance by limiting how often and in what quantities they prescribe these drugs, a practice called antibiotic stewardship.

“Our results offer another avenue for healthcare providers to protect patients from harm caused by unnecessary antibiotic use and address the rise of drug-resistant strains of microbes,” said study co-lead author Anna Brinks, BA, a medical student at NYU Grossman School of Medicine.

“Alopecia can have a devastating effect on self-image and can lead to social judgment, depression, and anxiety,” added study co-senior author Kristen Lo Sicco, MD. “Studies that advance the management of these conditions are critical to addressing not only hair loss itself, but also the psychological and social consequences that accompany it.”

Dr. Lo Sicco, an associate professor in the Ronald O. Perelman Department of Dermatology at NYU Grossman School of Medicine, says that the researchers next plan to repeat their work in a larger and more diverse group, as the study patients were mostly White.

In addition, she says the team intends to explore the triggers that cause lymphocytic scarring alopecia, which remain poorly understood.

Reference: Needle C, Brinks A, Pulavarty A, et al. Efficacy and tolerability of low-dose versus high-dose doxycycline in the management of lymphocytic scarring alopecias. J Am Acad Dermatol. doi: 10.1016/j.jaad.2025.02.028

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