Pathomechanism of Adverse Reactions to Biological Treatment of Inflammatory Skin Conditions

ABSTRACT Biological agents are widely used across medicine, including for immune‐mediated skin conditions such as psoriasis and atopic dermatitis. When used to treat a relevant pathological process, they demonstrate impressive efficacy and credible safety, helping to achieve remission and improved function and quality of life. However, with their expanded use, awareness and understanding of adverse reactions to biologicals have also increased. Herein, we discuss the pathomechanism of adverse reactions to biological agents used to treat skin conditions and apply these to Pichler's classification system. This classification differentiates five distinct types, namely overstimulation (type α), hypersensitivity or immunogenicity (β), immunodeviation (γ), cross‐reactivity (δ) and nonimmunologic adverse reactions (ε). This classification covers most types of adverse reactions associated with use of biological agents and could be used to better understand the reaction pathogenesis and manage the clinical features of biological adverse effects.