Using the population, intervention, comparator, outcomes, and study (PICOS) design framework, studies of patients with psoriasis, psoriatic arthritis, hidradenitis suppurativa, and atopic dermatitis treated with biologics targeting tumor necrosis factor-α (TNF-α), interleukin (IL)-12/23, IL-17, IL-23, or IL-4/13 were included. This evidence concerns the gene IL4 and atopic eczema.