Table 1 Conditions to consider in the differential diagnosis of urticaria

Urticarial vasculitis

∙ Lesions are usually painful (rather than pruritic), last > 48 h, and leave discoloration on the skin

Systemic mastocytosis

∙ Rare condition that involves the internal organs (liver, spleen, lymph nodes, bone marrow), in addition to the skin

Atopic dermatitis

∙ Chronic, highly pruritic inflammatory skin disease

∙ Clinical manifestations vary with age

Bullous pemphigoid

∙ Chronic, autoimmune, blistering skin disease

Erythema multiforme

∙ Acute, self-limited, skin condition characterized by discrete targetoid lesions

∙ Considered to be a type IV hypersensitivity reaction to certain infections, medications, and other various triggers

Familial cold autoinflammatory syndrome

∙ Rare, inherited inflammatory disorder characterized by recurrent episodes of rash, fever/chills, joint pain, and other signs/symptoms of systemic inflammation triggered by exposure to cooling temperatures

∙ Onset usually occurs during infancy and early childhood and persists throughout the patient’s life

Fixed drug eruptions

∙ Lesions occur from exposure to a particular medication and occur at the same site upon re-exposure to the offending medication

∙ Lesions usually blister and leave residual pigmentation

Subacute cutaneous lupus erythematosus

∙ A non-scarring, photosensitive skin condition

∙ May occur in patients with systemic lupus erythematosus (SLE) and Sjögren syndrome

Pruritic urticarial papules and plaques of pregnancy

∙ Benign skin condition that usually arises late in the third trimester of a first pregnancy

Muckle-Wells syndrome

∙ Rare genetic disease that causes hearing loss and recurrent hives

∙ May lead to amyloidosis

Schnitzler's syndrome with monoclonal IgG kappa gammopathy

∙ Rare disease characterized by chronic, non-pruritic hives, periodic fever, bone and joint pain, swollen lymph glands and an enlarged spleen and liver