There are four JAK subtypes: JAK1, JAK2, JAK3, and tyrosine kinase 2 (TYK2). Small molecule Janus tyrosine kinase (JAK) inhibitors can inhibit a variety of pro-inflammatory cytokines. Baricitinib is the first generation of JAK1/2 inhibitor targeting the ATPase of JAK, which blocks the intracellular transmission of cytokines through JAK-STATs. Thus far, it has been approved for the treatment of rheumatoid arthritis (RA); however, an increasing number of studies have suggested that baricitinib can be used to treat dermatological diseases, such as atopic dermatitis (AD), psoriasis, vitiligo, and alopecia areata. Baricitinib can be a new choice for the treatment of dermatological diseases, which cannot be treated with conventional drugs. We reviewed the application, efficacy, side effects, precautions, limitations and prospect of baricitinib in atopic dermatitis, psoriasis, vitiligo and alopecia areata (AA) in recent 5 years including clinical trials and case reports. Among them, the application in the field of alopecia areata is the most encouraging, and we reviewed the mechanism in detail.
