Acute urticaria Acute urticaria can be classified further as either allergic or non-allergic. Allergic is less common and may be an allergy to an ingested substance, e.g. a food or medicine, through a sting or through contact with a substance such as latex. Usually the allergic response will be mild requiring no emergency care; however sometimes the allergy may result in anaphylactic shock requiring emergency care and an injection of adrenaline. Non-allergic causes of acute urticaria are much more common and include: - Infections such as sinusitis, helicobacter, viral hepatitis;
- Serum sickness due to blood transfusions, viral illness or certain drugs (this is accompanied by other symptoms including sickness, fever, joint pain and swollen lymph glands);
- Certain medicines such as morphine (and other opiates), codeine and radiocontrast agents can cause a non-allergic release of mast cell granules such as histamine. Aspirin and other non-steroidal anti-inflammatories can also produce urticaria but through the production of leukotrienes which are potent mediators of immediate hypersensitivity reactions and inflammation;
- Non-allergic food reactions can be caused by salicylates in fruit (which are highest in berry and dried fruits but occur in most fruits), azo food dye benzoate preservatives (New Zealand Dermatological Society Incorporated, 2009).
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