Anaphylaxis is a severe, potentially life-threatening allergic reaction that occurs rapidly after exposure to an allergen. It is a medical emergency that requires immediate attention.
Causes of Anaphylaxis:
Anaphylaxis is often triggered by allergens such as:
- Foods: Peanuts, tree nuts, shellfish, eggs, milk, etc.
- Medications: Penicillin, aspirin, or other drugs.
- Insect stings: Bees, wasps, hornets.
- Latex: Found in some medical or household products.
Symptoms of Anaphylaxis:
Symptoms typically occur within minutes but can sometimes appear after hours. They include:
- Skin reactions:
- Hives, itching, or flushed skin.
- Swelling, especially of the face, lips, tongue, or throat.
- Respiratory problems:
- Difficulty breathing or wheezing.
- Tightness in the chest or throat.
- Cardiovascular symptoms:
- Rapid or weak pulse.
- Low blood pressure, which can cause dizziness or fainting.
- Digestive issues:
- Nausea, vomiting, or diarrhoea.
- Abdominal pain.
- Neurological effects:
- Anxiety, confusion, or loss of consciousness.
Emergency Treatment:
- Epinephrine: The first-line treatment is an injection of epinephrine (e.g., using an EpiPen).
- Call 999: Immediate medical attention is crucial.
Prevention:
- Avoid known allergens.
- Carry an epinephrine auto-injector if you’re at risk.
- Wear medical alert jewellery to inform others about your condition.
Anaphylaxis is diagnosed based on a combination of clinical evaluation, symptoms, and, in some cases, lab tests. The process involves the following steps:
1. Clinical History
- Trigger Exposure: A history of exposure to a potential allergen, such as foods (e.g., peanuts), medications, insect stings, or latex.
- Rapid Onset: Symptoms typically appear within minutes to hours of exposure.
- Prior Reactions: A history of similar, less severe allergic reactions can be a clue.
2. Symptoms
Diagnosis is based on the presence of symptoms involving multiple organ systems, such as:
- Skin: Hives, flushing, itching, or swelling.
- Respiratory: Shortness of breath, wheezing, throat tightness, or stridor.
- Cardiovascular: Hypotension, dizziness, or fainting.
- Gastrointestinal: Vomiting, diarrhoea, or abdominal pain.
- Neurological: Confusion or altered consciousness (due to low blood pressure or hypoxia).
The World Allergy Organization defines anaphylaxis based on any one of the following criteria:
- Acute onset of symptoms (skin/mucosal + respiratory or cardiovascular compromise).
- Two or more systems involved after exposure to a likely allergen.
- Hypotension after exposure to a known allergen (alone).
3. Physical Examination
- Focuses on identifying hallmark signs such as:
- Swelling of the face, tongue, or throat.
- Difficulty breathing or wheezing.
- Hypotension or shock.
4. Diagnostic Testing
While laboratory tests are rarely performed during acute episodes, they may help confirm anaphylaxis retrospectively:
- Serum Tryptase: Elevated levels (peaks 1-3 hours after onset) indicate mast cell activation.
- Histamine Levels: Rise shortly after symptoms but clear quickly.
- Allergen-Specific IgE Testing: Identifies the specific trigger after recovery using blood or skin-prick tests.
5. Differential Diagnosis
- Doctors must rule out conditions that mimic anaphylaxis, such as panic attacks, asthma exacerbations, or vasovagal syncope.
More information is available on the NHS website.
