Anaphylaxis is an acute systemic (multi-system) and severe type I hypersensitivity allergic reaction

What is Type 1 reaction

In the event of first exposure to Antigen, plasma cells secrete IgE which binds to Fc receptors on the surface of tissue mast cells and blood basophils.

Mast cells and basophils coated by IgE are "sensitized."

Later exposure to the same allergen, cross-links the bound IgE on sensitized cells resulting in degranulation and the secretion of pharmacologically active mediators such as histamine, leukotriene (LTC4 and LTD4), and prostaglandin that act on the surrounding tissues.

The main actions of these products are vasodilation and smooth-muscle contraction.

Causes

• Insect bites
• Foods (eg, peanut allergy)
• Drugs and IV infusions (Blood, Abx, Vaccines, Iron,,etc)

Presentation

with or without particular allergic exposure Hx

• Skin manifestations ( skin rash, urticaris, angio oedema,)
• Laryngeal obstruction
• Bronchospasm
• tachycardia
• hypotension and shock

Management

• secure ABC
• IM Adrenaline 1mg 1;1000
• IV Hydrocortisone 200 mg
• IV chlorpheniramine 10 mg
• consider nebs if brochospasm
• PO steroid and chlorpheniramine need to be continued

Further management

• find out the cause of anaphylaxis