We found no systematic reviews and no RCTs. We found a single partially controlled case series of 112 patients with patchy alopecia areata covering <25% of the scalp. Seventy-two patients with a total of 237 lesions received a 2-3-second application of a cotton swab dipped in liquid nitrogen.38 Two freeze-thaw cycles were applied once weekly for 4 weeks. New hair growth was seen in over 60% of the involved area in over 97% of patients treated with liquid nitrogen, which was statistically significant compared with the results of the non-treatment group.
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