Urticaria Rash

Urticaria rash

        The lesion of urticaria is due mainly to edema and secondary to localized vasodilation with increased capillary permeability. These changes are induced by chemicals which are vasoactive mediators (histamine, serotonin, acetylcholine, kinins, etc.).. These vasoactive mediators are released into the body at the target cells ,degranulation of urticaria: the mastocyte and polynuclear basophils. This degranulation to release histamine is the dependence of several stimuli: Allergy is type 1 (immediate hypersensitivity).

        The introduction into the body of allergens (pollen, insect stings, nuts, fish etc. ...) induces the formation of antibodies that are specific immunoglobulin E (IgE). They are able to bind to receptor on the membrane of mast cells and basophils. When the allergen is reintroduced a second time in the body (inhalation, ingestion, intramuscular, dermal application), the molecule antigen (allergen) binds to the IgE adhering to the mast and basophilic. This triggers an explosive degranulation target cells. Then there is release of histamine and "slow reactive substance of anaphylaxis (SRS-A).

        This allergic reaction can be:

• Generalized: Anaphylactic shock;
• Located: asthma, urticaria.

        The complement system (allergic type 2I) is a chemical that acts as a nonspecific immune mediator. It consists of twenty blood proteins (C1, C4, C2, C3, etc..) that interact with each other. These proteins, once activated, promote the recognition and elimination of foreign molecules into the body. The complement activation causes the release of two proteins C3a and C5a which are able to bind to the surface of mast cells and basophils and to degranulation.

The drug rash in urticaria

        Drugs are responsible for 30 to 50% of urticaria. The route of introduction may be oral, rectal, parenteral, dermal, vaginal or respiratory. Sometimes, the drug is so commonplace that the patient forgets to say to the doctor: sleeping pill, vitamins, laxatives, nasal drops, eye drops, ointments, toothpaste, eggs, copper coil. Most often, an acute urticaria appears within minutes or hours after drug administration: common urticaria, angioedema, with or without anaphylactic shock. Sometimes the symptoms are delayed a few days.Rarely, the trend is towards a persistent chronic urticaria despite the withdrawal of the drug.

        All drugs can cause urticaria. However, some of them are most often invoked.

• Antibiotics: sulphonamides, penicillin and derivatives (ampicillin, methicillin, cloxacillin, carbenicillin, cephalosporins). Inputs whith masked penicillin (meat, dairy products ...) are factors of sustainability of urticaria. Even though medicamentation is absolutely necessary, these antibiotics are still prescribed with caution.
• The analgesic and anti-inflammatory drugs like aspirin, activates the release of histamine by blocking the synthesis of prostaglandins. Patients sensitive to aspirin also have urticarial reactions with indomethacin (indocid) and some additives (tartrazine, benzoic acid ...). Other products may be involved in hives: antipyrine, pyramidon, phenacetin, paracetamol, amidopyrine, phenylbutazone etc. ...
• Drugs histamino liberators: colimycine, polymyxin B, quinine, morphine, codeine, atropine, beta blockers, curare, dextran, horse serum, thiamine, hydralazine ...
• Other that cause urticaria: anticoagulants, enzymes (chymotrypsin), animal hormones (ACTH, insulin, thyroid extracts), iodinated contrast materials, serotherapy, metals (prosthesis containing nickel, copper IUDs, dental amalgams based mercury)

Urticaria rash pictures