七年制医学课件 皮肤病学 5Urticaria.ppt

Urticaria ShanKui MD Definition These are wheals, white or red evanescent plaques generally surrounded by a red halo or flare. Etiology 1. Food The most allergenic foods are shellfish, shrimps, crab, chocolate, nuts, peanuts, tomatoes, strawberries, melons, pork, cheese, garlic, onions, and spices. Eggs and milk always induce urticaria in children. 2. Medicines Many medicines can start urticaria by allergy, the most common drugs are as follows: penicillin, serum, vaccine, furazolidone, sulfanilamide and so on . Sometimes a few drugs can directly stimulate mast cells to produce histamine, like aspirin, morphine, codeine, quinine, etc. 3. Infections Infections caused by all organisms are another possible reasons to induce urticaria. The most common organism is virus of upper respiratory and staphylococcus aureus. Chronic infections of the patients cannot be easy verified as the pathogen of urticaria; it must be tested by therapy. 4. Physical factors: Cold, hot, sunlight, friction and pressure 5. Animals and plants : Urticaria can be induced by animals fur skin or pollen or stinging of insects. 6. Spirit factors: In some cases, stress can trigger urticaria, but in another cases stress may lead to histamine releasing. 7. Diseases of internal organs Rheumatic disorder, rheumatoid arthritis, systemic lupus erythema, malignant tumor, disorder of endocrine and some others can be another reasons of urticaria. Pathogenesis 1.Allergy The wheal results from increased capillary permeability, which allows proteins and fluids to extravasate. Capillary permeability results from the increased release of histamine from the mast cells situated around the capillaries. Allergy The mast cell is the primary effector cell in urticarial reactions. The mast cell granules containing heparin and histamine disappear or almost disappear during wheal, and then degranulated. Mast cell mediators can cause activation and recruitment of eosinophils, ne