Patients who are afflicted by the condition known as alopecia areata -- patchy hair loss -- should understand that there is "no reliable, safe, effective, long-term treatment," said review co-author Dr. Mike Sladden, a dermatologist and senior lecturer at the University of Tasmania in Australia.

Alopecia areata accounts for an estimated one in every 50 dermatologist visits in the United States and the United Kingdom, and one study suggests that 1.7 percent of people will be afflicted by it during their lives.

The condition often causes patchy hair loss; meaning hair in some parts of the body falls out while remaining in others. In some cases, however, affected patients can lose all of their scalp hair or even all of their body hair.

Most affected people begin developing bald spots before the age of 20. Many cases of alopecia areata get better over time, although hair loss often returns.

Research suggests that alopecia areata is caused when the immune system attacks the hair follicle. Some cases are linked to physical or emotional stress, but others do not have an apparent trigger.

In the new review, Sladden and colleges examined 17 randomized controlled trials of treatments for alopecia areata.

The review appears in a recent issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews like this one draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.

The studies, which looked at 540 patients, measured the effectiveness of several treatments, including topical and oral corticosteroids and topical cyclosporine. These drugs dampen the immune system to try to stop it from becoming confused and attacking the body.

Other treatments examined in the studies include photodynamic therapy (which exposes the skin to light) and topical minoxidil (Rogaine).

The researchers could not find any randomized controlled studies of other treatments, including diphencyprone, dinitrochlorobenzene, intralesional corticosteroids and dithranol.

According to the review, none of the studies showed long-term "beneficial hair growth" -- the return of more than half of the missing hair.

"Few treatments for alopecia areata have been well evaluated in randomized trials and we found none that addressed participant-focused measures of success or measurements of quality of life," the review authors wrote.

The reviewers had hoped to look at 11 other studies, but were not able to do so. In some cases, the researchers could not obtain copies of the studies. In others, the studies have not yet been published.

One small, unpublished study found that hair regrew in almost half of 60 subjects who applied onion juice to their heads. They all had mild cases of the condition affecting less than a quarter of their heads. Onion juice, an alternative medicine, has been used to treat infections.

Sladden said patients should balance their desire to resolve their hair loss with the risks of the available treatments.

"Although there is no proven treatment, some people might choose to try a 'safe' treatment -- such as a topical steroid -- even in the absence of good evidence of the treatment's benefit," he said. "Doctors and patients need to talk openly about the condition and discuss treatments and likely outcomes. And they need to avoid those treatments which might be harmful."

Dr. Amy McMichael, an associate professor of dermatology at Wake Forest University School of Medicine, said there has been little high-quality research because no agencies are willing to pay hundreds of thousands of dollars to study a nonfatal disease that affects the skin and hair.

Still, many of the available treatments do work very well in some cases, she said. However, "there is no way to predict who will respond to treatment or how long the response will hold."

Another dermatologist, Dr. Paradi Mirmirani of the Permanente Medical Group in Vallejo, Calif., said patients should not be discouraged by the review findings or assume that "nothing works."

"It's true if they do nothing, the hair may spontaneously regrow," Mirmirani said. "But there are treatment options that they should at least discuss with a physician."

Reference: Delamere FM, et al. Interventions for alopecia areata (Review). Cochrane Database of Systematic Reviews 2008, Issue 2.

Note: If no author is given, the source is cited instead.

• Hair Loss
• Hearing Loss
• Diseases and Conditions
• Today's Healthcare
• Men's Health
• Human Biology

• Baldness
• Hair follicle
• Baldness treatments
• Dandruff
• Evidence-based medicine
• Clinical trial