Erythema refers to redness of the skin that blanches under pressure. It can be diffuse or localized and can be caused by drugs, infections, autoimmune diseases, or idiopathic factors. Erythema multiforme is an acute, self-limited mucocutaneous syndrome characterized by target lesions that can be caused by infections like herpes or drugs. Toxic epidermal necrolysis is a severe mucocutaneous reaction that may be drug-induced and can involve extensive skin and mucosal detachment. Urticaria refers to transient wheals and hives on the skin that are usually itchy. Chronic urticaria lasts more than 6 weeks and can be