Anaphylaxis is a severe, potentially life-threatening allergic reaction that can develop rapidly. It occurs when the immune system overreacts to an allergen, triggering a cascade of inflammatory responses. Symptoms can include difficulty breathing, swelling, hives and shock. Prompt administration of adrenaline is crucial for managing anaphylaxis.
Pathophysiology
1. IgE-Mediated Response
- Upon exposure to an allergen, the immune system produces antibodies called IgE. These antibodies bind to mast cells and basophils, which are immune cells found throughout the body, especially in areas like the skin, lungs and gastrointestinal tract.
2. Mast Cell Degranulation
- When the allergen binds to IgE on mast cells and basophils, it triggers a process called degranulation. This process causes the release of preformed inflammatory mediators stored within these cells.
3. Inflammatory Cascade Triggered by Mediators
- The released mediators cause widespread inflammation, affecting various organ systems. Some of the key mediators involved in anaphylaxis include:
- Histamine: Causes blood vessel dilation, smooth muscle contraction, and increased mucus production.
- Tryptase: Breaks down proteins and contributes to tissue damage.
- Leukotrienes: Cause bronchoconstriction, inflammation, and mucus production.
- Prostaglandins: Dilate blood vessels and contribute to inflammation.
- Cytokines: Signal other immune cells to join the inflammatory response.
4. Systemic Manifestations
- Depending on the amount of mediators released and the individual’s sensitivity, different organ systems can be affected, leading to various symptoms:
- Respiratory system: Difficulty breathing, wheezing, coughing and chest tightness.
- Cardiovascular system: Shock (a life-threatening drop in blood pressure), rapid heartbeat and fainting.
- Skin: Hives, itching and flushing.
- Gastrointestinal system: Nausea, vomiting, diarrhoea and abdominal pain.
- Nervous system: Anxiety, dizziness and confusion.
5. Positive Feedback Loop
- Some of the released mediators can further activate other immune cells, creating a positive feedback loop that amplifies the inflammatory response. This can lead to a rapid escalation of symptoms.