Clinical trial to evaluate the safety and efficacy of ablative fractional CO2 laser in the treatment of mild to moderate alopecia areata in Chinese adults

INTERVENTION: control group:minoxidil solution treatment of treatment of alopecia areata;experimental group:ablative fractional CO2 laser treatment of alopecia areata; CONDITION: alopecia areata PRIMARY OUTCOME: Target Area Hair Counts; SECONDARY OUTCOME: Hair growth situation;Target Area Hair width; INCLUSION CRITERIA: 1. Chinese mild‐to‐moderate alopecia areata patients aged 18 to 65 years(stable period), the current duration of scalp hair loss is at least 6 months, and the longest is not more than 5 years; there is no evidence of natural final hair regeneration within the past 3 months ; 2. According to the Salt score: 5%‐49% of patients with scalp area involvement; 3. Agree to follow the experimental treatment plan and visit plan, join the group voluntarily, and sign the informed consent in writing; 4. Willing to use the same shampoo throughout the test and keep the same hairstyle, color and length.