IL17A and psoriasis: In addition, another reason why blocking IL-17 has a relatively greater impact than blocking IL-23 may be that IL-17 is essential for fighting against infections by pathogenic bacteria such as Staphylococcus aureus and Candida albicans on the skin, and therefore biologics targeting IL-23 may be a better choice for patients with psoriasis in terms of drug compliance and safety [25, 26].