Allergic urticaria

This code identifies an acute or chronic skin condition characterized by the sudden appearance of intensely itchy, raised, red welts (hives) on the skin, directly triggered by an allergic reaction. These lesions, known as wheals, can vary in size and shape and often blanch with pressure. The underlying mechanism involves the release of histamine and other mediators from mast cells due to an immune response to an allergen.

Assign this code when documentation clearly indicates urticaria is caused by an identifiable allergic trigger, such as food, medication, insect stings, or environmental allergens. This code is appropriate for both initial and subsequent encounters where allergic urticaria is the primary diagnosis or a significant co-morbidity. Supporting documentation should specify the allergic etiology.

• Do not use this code for urticaria of unknown origin; instead, consider codes for idiopathic urticaria.
• If the specific allergen is identified, consider an additional code from Z88.- (Allergy status to drugs, medicaments, and biological substances) or Z91.0- (Allergy status to food, other antigenic substances, and animal dander) for more specificity.
• Distinguish from contact dermatitis, which involves skin inflammation from direct contact with an irritant or allergen, but typically presents with different lesion morphology.