A-Z page index

A B C D E F G H I J K L M N
O P Q R S T U V W X Y Z

Translate DermNet NZ

from English to German English to Spanish English to French English to Italian English to Portuguese English to Russian BETA English to Arabic BETA English to Japanese BETA English to Korean BETA English to Chinese (S) BETA

Buy skin care products

Search for books

Anaphylaxis

Anaphylaxis is a severe allergic reaction that results from the interaction of an allergen (see causes below) with specific immunoglobulin E (IgE) antibodies bound to mast cells in the skin and lungs and basophils in the blood. The mast cell releases chemicals that act on blood vessels to produce a wide range of clinical effects throughout the body.

Full-blown anaphylaxis includes urticaria (hives) and/or angioedema (tissue swelling) with hypotension (low blood pressure) and bronchospasm (asthma).

Anaphylactoid reactions are clinically similar to those experienced in anaphylaxis. The only difference is that anaphylactoid reactions are non-IgE mediated and may be less severe.

Severity of reactions from anaphylaxis can vary from mild symptoms to sudden death. In any case, medical attention should be sought immediately and appropriate treatment given.

Urticaria

What causes anaphylaxis?

A wide variety of substances can cause anaphylaxis or anaphylactoid reactions. Approximately one third of all cases have no known cause (idiopathic).

What are the signs and symptoms of anaphylaxis?

Food-induced anaphylaxis often produces skin reactions and respiratory symptoms whilst drug- or venom-induced anaphylaxis more often produces shock. Symptoms usually occur within 5-60 minutes of contact with the allergen, but sometimes occur after several hours, or even 3-4 days later. Fast onset and rapid progression of symptoms usually indicates severe, life-threatening anaphylaxis. One or more organ systems may be involved. Typical features include:

Diagnosis of anaphylaxis

Because acute anaphylaxis can be immediately life threatening, diagnosis must be made quickly and efficiently, often while administering initial medication. Diagnosis is essentially made on the basis of:

• Typical symptoms and signs, involving at least two organ systems
• Development of specific symptoms after exposure to a known allergen
• Exclusion of other diseases that may have similar signs and symptoms

What is the treatment of anaphylaxis?

Acute anaphylaxis must be treated as a medical emergency with stabilisation of airway, breathing and circulation. Intramuscular adrenaline (epinephrine) must be given immediately to patients with signs of shock, airway swelling, or definite difficulty in breathing. This is followed by treatment with an antihistamine, corticosteroid and perhaps other drugs.

Adrenaline may not be necessary for skin manifestations of anaphylaxis. Treatment with antihistamines may be all that is required.

Prevention is the best medicine. All those at risk of anaphylaxis should wear a Medic Alert/emergency bracelet with full details of allergies and contact details of their doctor. In some cases, a patient or caregiver should always carry an emergency kit containing self-injectable adrenaline (e.g. Epipen) and antihistamine tablets.