Anaphylaxis

In this post, you are going to learn what anaphylaxis means, anaphylaxis shock, reaction, symptoms and treatment

What is anaphylaxis (anaphylactic reaction) ?

Anaphylaxis is a life-threatening response on exposure to a specific chemical, food or animal. These chemicals food or animals that causes anaphylaxis are called allergens. In the classic form of anaphylaxis, the individual must have been initially exposed to the allergen and sensitized such that at the next exposure, the person would have an anaphylactic reaction to the allergen which occurs within minutes of exposure. Sensitization means that the body has produced specific proteins (called antibodies) against a particular allergen. Anaphylaxis is a type I hypersensitivity reaction.

Anaphylaxis versus anaphylactoid reaction

Anaphylaxis is an immunologic reaction that is IgE mediated and therefore requires prior sensitization before it occurs. It is the binding of immunoglobulin E to the allergen that brings about the release of cells (mast cells and basophils) that release chemicals which cause anaphylaxis. In contrast, anaphylactoid reactions are non-immunologic and would result in direct release of basophils (a type of white blood cell) and mast cells which release chemicals that cause all the symptoms. Allergens that cause anaphylactoid reactions such as contrast media and opioids do not require a prior exposure/sensitization to elicit the reaction.

anaphylaxis
anaphylaxis-Credit: Designua/shutterstock

What causes anaphylaxis reaction?

Classically, anaphylaxis occurs following an initial exposure and sensitization such that when next that individual is exposed to the allergen, the antibody (immunoglobulin E or IgE) binds to the allergen resulting in the release of specific white blood cells called basophils and other cell that release chemicals which cause swellings, constriction of muscles in the respiratory and gastrointestinal systems as well as the skin and blood vessels.

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Allergens that may cause anaphylaxis include:

  • Foods such as peanuts, milk, seafood, eggs, gelatin in drug capsules, beans
  • Venoms from bee, wasps, fire ants, hornets
  • Hormones-vasopressin, insulin, parathyroid hormone
  • Enzymes-Streptokinase, chymotrypsin, penicillinase
  • Pollen extract-trees, grass, ragweed
  • Non-pollen extracts-dust mites, animal dander (cats and dogs)
  • Antibiotics such as penicillin e.g. ampicillin, amoxicillin, cephalosporin e.g. cefuroxime, ceftriaxone; quinolone e.g. ofloxacin, ciprofloxacin;
  • Antifungal drugs such as amphotericin B
  • Antihypertensive medications such as ACE inhibitors e.g. Captopril, Lisinopril, Ramipril,
  • Local anaesthetic agents such as procaine, lidocaine
  • Chemotherapy agents such as paclitaxel, doxorubicin
  • Monoclonal antibodies e.g. omalizumab, natalizumab,
  • Non-steroidal anti-inflammatory drugs (NSAID) e.g. aspirin, indomethacin, diclofenac
  • Some vaccines
  • Contrast media (given during certain investigations such as CT scan, MRI and IVU)

What are the symptoms of anaphylaxis?

  • Difficulty in breathing (due to tightening of the windpipe which restricts airflow)
  • Noisy breathing on inspiration (stridor)
  • Noisy breathing on expiration (wheezing) if the lower airways are involved
  • Feeling of lump in the throat (due to swelling of the entrance to the windpipe-larynx)
  • Hoarseness of voice
  • Itching of the skin and throat
  • Skin rashes (round red skin rashes with a blanched centre –Urticaria)
  • Redness of the eyes
  • Swollen and warm skin
  • Angioedema
  • Sneezing
  • Nasal congestion
  • Cough
  • Catarrh
  • Dizziness
  • Weakness
  • Fainting
  • Palpitations
  • Chest pain
  • Nausea
  • Vomiting
  • Diarrhoea
  • Headache
  • Blurred vision

Anaphylaxis versus anaphylactic shock

When an individual with anaphylaxis is found to have blood pressure below 90/60mmHg in addition to any of the above mentioned symptoms, the person is said to be in anaphylactic shock. Anaphylactic shock is commonly seen with bee sting and wasp stings.

Anaphylaxis vs allergic reactions

Anaphylaxis is a type of allergic reaction referred to as type I hypersensitivity reaction. It is the most dreaded type of allergic reaction because it is potentially fatal within a few minutes of onset of symptoms. Other types of allergic/ hypersensitivity reactions include type II (complement mediated), type III (immune complex mediated), type IV (cell-mediated or delayed) hypersensitivity reactions.

How is anaphylaxis treated?

Early recognition of anaphylaxis is imperative because death may occur within a few minutes of symptoms onset.

Epinephrine may be administered immediately as this is an emergency. People who are known to have certain food allergies are prescribed epi needles or epi pens which should be administered immediately symptom of anaphylaxis is noticed. The patient should be taken to the emergency department of the nearest hospital for further treatment.

Treatment in the hospital includes the use of intravenous infusions, adrenaline/epinephrine, oxygen, steroids, and bronchodilator drugs. In severe cases, the individual may need to be managed in the intensive care unit (ICU).

Anaphylaxis prevention

Prevention is better than cure. It is important to identify the cause and subsequently avoid exposure to it. Skin prick testing or scratch test before administration of drugs that are known to cause anaphylaxis if it is absolutely necessary to administer that particular agent. A positive skin prick test would produce an urticarial wheel and flare within 20 minutes of the test and resolves within 2 hours.

Avoid or modify outdoor activities to prevent being stung by a bee, wasp or hornet. Avoid eating in areas where insects are attracted. Avoid wearing perfumes that may attract insects to you. Cut grasses around your environment, dispose refuse and fruits on the floor under trees.

Inform your doctor or pharmacist if you have ever had anaphylactic reaction to any medication or food. Also inform the waitress in any restaurant when eating out if you have any food allergies.

About the author

Doctor

Grace is an internist currently practising in Nigeria. She has gained experience practising both in the private and public health sectors over the last ten years. She is passionate about giving patients adequate information about their health conditions. She believes that a large part of the management of chronic diseases lies with patients' understanding of their illnesses and the need for lifestyle modifications and medications.