Causes of Chronic Urticaria

No exact external or environmental trigger has yet been found for most cases of chronic urticaria. For decades, physicians and non-physicians alike have often attributed urticaria of all types to “stress” or “nervousness.” While stress can certainly worsen or trigger urticaria in some people, it is now known that the cause of urticaria may be more complex and not usually caused by stress, anxiety, or psychological factors.

In some individuals, chronic hives are the result of the individual producing antibodies against his/her own tissues and not due to any external factors or a specific allergy. In approximately 25% of people with chronic urticaria, laboratory tests reveal an antibody against a receptor on the mast cell (an allergy-related cell that is present in the skin.) Antibodies can trigger releases of substances from the mast cell such as histamine that induces redness, itching and swelling. Research shows that some individuals with chronic urticaria share similar genetics with people who have autoimmune diseases such as rheumatoid arthritis. It is also known that people with chronic urticaria are more likely than people in the general population to have antibodies against the thyroid gland. Thyroid antibodies can cause hypo- or hyper-thyroidism (under or overactive thyroid). Several studies have shown that people with chronic urticaria associated with thyroid antibodies had improvement in their urticaria when treated with thyroid hormone. This therapy is reserved for unusually difficult-to-treat urticaria. It is important to note that most people with chronic urticaria DO NOT have any other autoimmune disease and except for their hives are otherwise completely healthy.

Common Causes of Hives:

Allergy: medications
Nonimmunologic reactions to medications (aspirin, morphine, codeine, medication used in anesthesia) and intravenous contrast dyes
Infections: especially viral infections including mononucleosis and hepatitis B
Autoimmune disease: SLE (lupus), vasculitis, serum sickness disease, other underlying medical problems including production of antibodies against cancer cells
Contact urticaria due to direct contact with an allergen (food, plants, animal saliva, medication, etc.)
Idiopathic urticaria: hives in which no cause has been identified
Physical urticaria