What are non-allergic causes of urticaria?

• Infections: sinusitis, Helicobacter (a cause of stomach ulcers), dental abscess, viral hepatitis, mycoplasma penumonia, infectious mononuclosisand candida • Serum sickness, due to blood transfusion, viral infection or medicines (e.g. Ceclor™); urticaria is accompanied by fever, swollen lymph glands, painful joints and nausea. It is thought to result from immune complexes of the allergen and antibodies lodging in small blood vessels • Non-allergic release of mast-cell granules by medicines, especially morphine, codeine, other opiates, and radiocontrast agents. Urticaria provoked by aspirin and other NSAID’s usually involves leukotriene formation, although allergy involving IgE antibodies may also occur with aspirin • Non-allergic food reactions, from salicylates in fruit, azo dye food colouringagents, benzoate preservatives and other food additives, or from histamine due to bacterial decomposition e.g. scombroid fish poisoning