An episodic, vascular, rapidly occurring, usually self-limiting cutaneous reaction to systemic allergens, involving only the superficial portion of the dermis. The condition is characterized by a sudden, general eruption of transient, pale pink, raised, edematous wheals surrounded by a red flare, which are associated with severe itching. Urticaria is also known as hives.

The condition may be due to a variety of stimuli. Uticaria may be caused by an anaphylactic reaction limited to the skin, or it may occur as a result of contact with an external irritant or allergen. Causative factors may include: physical agents; insect stings or bites; desensitization injections; pollens; ingestion of foods, such as eggs, shellfish, or nuts; medications; or neurogenic factors. Urticaria may also be a symptom of viral infections, such as hepatitis, infectious mononucleosis, and rubella. Histamine may also cause the condition, resulting in erythema, wheals, and flaring due to dilation of blood vessels on the outermost area of the wheals.

Spontaneously occurring, wheals vary in size and shape and may occur throughout the body. Itching is usually the first sign. Urticaria develops rapidly after exposure to allergens, and the time that it lasts may vary.

In general, the cause of urticaria is obvious and, as a result, diagnostic tests are rarely required because of the self-limiting, nonrecurrent nature of the reaction. If chronic urticaria develops, a careful history, physical examination, and identification of exposure to possible offending agents, such as physical agents, medications, or foods may be helpful in the diagnosis. Skin patch testing may be performed by applying allergens to the skin to identify the causative or sensitizing agent. Laboratory tests may include a complete blood count (CBC), urinalysis, and erythrocyte sedimentation rate, along with chest x-ray to rule out infections.

The best treatment is elimination of the causative agent, if it can be identified. If no preventable cause can be identified, the treatment is symptomatic. Antihistamines may be effective in most cases. In severe cases that do not respond to antihistamines, corticosteroids may be used. Treatment may also include desensitization to an allergen by giving intradermal injections of progressively larger doses of specific antigens that were identified by skin testing.

Skin abrasion or secondary infections may occur as a result of scratching.

Per 38 CFR 3.380, Diseases of allergic etiology, including bronchial asthma and urticaria, may not be disposed of routinely for compensation purposes as constitutional or developmental abnormalities. Service connection must be determined on the evidence as to existence prior to enlistment and, if so existent, a comparative study must be made of its severity at enlistment and subsequently. Increase in the degree of disability during service may not be disposed of routinely as natural progress nor as due to the inherent nature of the disease. Seasonal and other acute allergic manifestations subsiding on the absence of or removal of the allergen are generally to be regarded as acute diseases, healing without residuals. The determination as to service incurrence or aggravation must be on the whole evidentiary showing. 

For the purposes of this diagnostic code, chronic urticaria is defined as continuous urticaria at least twice per week, off treatment, for a period of six weeks or more