Allergic reactions range from a nuisances to life-threatening conditions. Anaphylaxis is the most severe type. It is characterized by the ABC criterion of disturbance to the airway, breathing, and/or circulation. It generally occurs within 30 minutes of exposure to an ingested or injected allergen. Common causes are antibiotics, anesthetic agents, other drugs, nuts, seafood, and insect stings. Inhaled allergens such as pollens may cause severe asthma, but rarely anaphylaxis.
It is difficult to predict who is at risk for anaphylaxis. Different patients with the same immunoglobulin E (IgE) can be exposed to the same allergen, and one may suffer anaphylaxis while another has only a local reaction, and a third no reaction at all. According to the medical literature, there is a public perception that the severity of allergic reactions gets worse with each exposure, but this is not true. Fatal anaphylaxis occurs typically in patients who have had only mild, if any, allergic reactions to the guilty substance. However, patients who survive an episode of anaphylaxis should be evaluated by an allergist or immunologist to minimize the risk of future episodes.
Many different organ systems can be affected by anaphylaxis:
1. Skin: Possible symptoms include itching, weals (urticaria), and swelling
2. Gastrointestinal: Nausea, abdominal pain, vomiting, and/or diarrhea
3. Respiratory: Cough, wheeze, bronchospasm, sneezing, runny nose, swelling of the throat and upper airway
4. Mouth: Swelling of the lips and tongue
5. Cardiovascular: Low blood pressure, with possible fainting, and chest pain
6. Other: Anxiety and an “impending sense of doom”.
The symptoms resemble asthma, cardiovascular events such as cardiogenic shock, and panic attacks.
The primary treatment is adrenaline. Some patients are prescribed autoinjectors, but these are not guaranteed to work. The patient may collapse before he/she can use it. One deceased patient was found holding an unused autoinjector. Others may forget to carry the autoinjector when needed, or to get it refilled promptly after use. In addition, the needles are generally too short to reach the muscle, and thus provide only a subcutaneous dose. Intramuscular or intravenous injections performed by a health care professional lead to more rapid absorption and higher concentrations in the blood. The risks of adrenaline include heart attack, cardiac arrhythmias, and hypertensive intracerebral bleeding.
Other treatments for anaphylaxis include fluids, antihistamines, and steroids. Other immune suppressive drugs are in clinical trials. Generally the patient should be positioned lying down. Oxygen may be needed.
Research continues into this devastating allergic reaction.
Reference:
El-Shanawany T et al, “Clinical Immunology Review Series: An approach to the patient with anaphylaxis”, Clinical and Experimental Immunology 2008; 153: 1-9.
Linda Fugate is a scientist and writer in Austin, Texas. She has a Ph.D. in Physics and an M.S. in Macromolecular Science and Engineering. Her background includes academic and industrial research in materials science. She currently writes song lyrics and health articles.