Urticaria occurs due to release of the chemical "histamine" and other factors from mast cells in the skin as a response to triggering agents.
This causes leakage of fluid from the capillaries, resultant swelling of the skin and relaxation of blood vessels leading to the inflammatory reaction.
Some causes of Hives (Urticaria) are:
- Foods: A large variety of foods can trigger urticarial reactions in people with strong sensitivities. Foods such as shellfish, peanuts, tree nuts, eggs, fish, and milk are the most common culprits.
- Medications: Virtually every medication has the potential to trigger hives or angioedema. However, the most common causes of Hives (Urticaria) are penicillin, aspirin, ibuprofen, naproxen and blood pressure medications.
- Common allergens: Other substances that commonly cause hives and angioedema are pollen, latex, animal dander, and insect stings.
- Environmental factors: Physical factors such as heat, cold, water, sunlight, pressure, exercise and emotional stress also figure among the causes of Hives (Urticaria).
- Underlying medical conditions: Certain illnesses such as thyroid conditions, bacterial and viral infections such as hepatitis, HIV, Cytomegalovirus or Epstein-Barr virus; cancers such as lymphoma, blood transfusions, etc are also known to trigger hives.
- Genetics: Hereditary angioedema is an inherited form of urticaria. It is known to occur due to low levels or abnormal functioning of certain components of the immune system.