Treatment with a drug normally used for a bone marrow condition had reversed baldness caused by alopecia in three patients, scientists in the US said.
The sufferers had lost at least a third of the hair on their heads, and each regained total hair regrowth within five months of being treated with ruxolitinib, which is approved in the United States and European Union for treatment of myelofibrosis.
One of the team from Columbia University medical centre, Professor Angela Christiano, has herself suffered from the condition, and described it as "not life threatening, but it is life altering".
The results are announced in the online edition of Nature Medicine, by the team from Columbia, who previously identified the immune cells responsible for destroying the hair follicles. The treatment would not work for male pattern baldness, which is linked to hormones.
The scientists tested two drugs on mice, where hair loss was completely reversed and the effects proved long lasting. They have gone on to test ruxolitinib on human patients.
Christiano said it was wrong to dismiss the condition as unimportant. "Patients with alopecia areata are suffering profoundly, and these findings mark a significant step forward for them," she said.
Alopecia areata, which typically causes patchy hair loss, is an autoimmune disease where the immune system attacks and destroys the hair follicles.
Of sufferers involved in the trial, all three showed hair regrowth after treatment with a twice daily tablet for up to five months. The team leader, Raphael Clynes, said: "We've only begun testing the drug in patients, but if it continues to be successful and safe, it will have a dramatic, positive impact on the lives of people with this disease."