TLDR Laser and light therapies, especially the 308 nm excimer laser, are effective and safe for treating alopecia areata, but more research is needed.
The document from 2017 reviewed the effectiveness and safety of laser and light-based therapies for treating alopecia areata (AA), a type of hair loss caused by an autoimmune response. The excimer laser, particularly the 308 nm monochromatic excimer light (MEL), was highlighted as an effective treatment, with studies showing 60 to 77% improvement in hair regrowth. Other treatments such as diode lasers also showed promise, with one study reporting hair regrowth in 94% of treated patches among 16 patients. However, therapies like narrowband UVB phototherapy and Nd:YAG lasers had limited success or were confounded by factors like spontaneous remission or concurrent treatments. UVA-1 phototherapy was noted for its safety and significant improvement in a small study of 4 patients. Side effects of these therapies were generally mild. The review emphasized the need for more randomized controlled trials with larger patient numbers and longer follow-up periods to establish the long-term efficacy and safety of these treatments and called for a universal measure of hair growth to objectively compare different treatments.
30 citations,
January 2015 in “Dermatology” 308-nm excimer laser therapy helps regrow hair in alopecia areata.
18 citations,
January 2015 in “International Journal of Trichology” Intralesional steroids are more effective for hair regrowth in alopecia areata than NBUVB, but combining them doesn't improve results.
81 citations,
August 2014 in “Lasers in Surgery and Medicine” Red light therapy is safe and effectively increases hair growth in women with hair loss.
[object Object] 37 citations,
November 2011 in “Photodermatology Photoimmunology & Photomedicine” Narrowband UVB phototherapy alone is not very effective for treating alopecia areata.
79 citations,
September 2009 in “Pediatric dermatology” The 308-nm Excimer laser is effective and safe for treating patchy alopecia areata in children.
64 citations,
June 2009 in “Photomedicine and Laser Surgery” Excimer light effectively treats various skin diseases, including psoriasis, vitiligo, and mycosis fungoides.
[object Object] 9 citations,
April 2009 in “Dermatologic surgery” Infrared light might help treat stubborn alopecia areata.
90 citations,
January 2009 in “Journal of cosmetic and laser therapy” Low-level laser therapy might help hair growth, but more research is needed.
63 citations,
January 2006 in “Journal of cosmetic and laser therapy” The pulsed infrared diode laser is effective for treating hair loss in alopecia areata.
45 citations,
January 2018 in “International Journal of Dermatology” Nail problems are common in people with alopecia areata, often leading to cosmetic and functional issues, but more research is needed for treatment guidelines.
16 citations,
November 2016 in “Journal of Cosmetic and Laser Therapy” Laser and light therapies, especially the 308 nm excimer laser, are effective and safe for treating alopecia areata, but more research is needed.
[object Object] 
71 citations,
March 2009 in “Seminars in cutaneous medicine and surgery” Alopecia areata can cause unpredictable hair loss, and treatments like corticosteroids and minoxidil may help but have varying side effects.
September 1998 in “Journal of the European Academy of Dermatology and Venereology” PUVA-turban therapy can help some people with severe alopecia areata regrow hair.
63 citations,
April 1985 in “Journal of the American Academy of Dermatology” Topical PUVA can cause temporary hair regrowth in some alopecia areata patients but doesn't change the long-term outcome.
