Allergy Basics: What Happens During an Allergic Reaction?

An allergic reaction occurs when your immune system overreacts to a foreign substance, known as an allergen. This happens when your body mistakes the allergen as a threat and launches a defense mechanism to protect itself. Here's a simplified explanation of what happens during an allergic reaction:

1. Exposure: You come into contact with an allergen through inhalation, ingestion, skin contact, or injection.

2. Activation: Your immune system identifies the allergen as foreign and activates certain immune cells, such as mast cells and basophils. These cells contain histamine and other inflammatory mediators.

3. Histamine Release: Upon activation, mast cells and basophils degranulate, releasing histamine and other mediators into the surrounding tissues.

4. Vasodilation and Permeability: Histamine causes dilation (widening) of blood vessels, resulting in increased blood flow to the affected area. This leads to swelling and redness. The increased blood flow also increases the permeability of blood vessels, allowing fluid to leak out and causing tissue swelling.

5. Mucus Production: Histamine stimulates the production of mucus in the respiratory tract, leading to a runny nose, sneezing, and congestion.

6. Muscle Contraction: In certain cases, histamine can cause the contraction of smooth muscles, resulting in symptoms like wheezing, coughing, or abdominal pain.

7. Secondary Effects: In severe allergic reactions (anaphylaxis), histamine and other mediators can have widespread effects throughout the body. This can lead to a sudden drop in blood pressure (hypotension), rapid pulse, difficulty breathing, nausea, and dizziness. Anaphylaxis can be life-threatening and requires immediate medical attention.

8. Resolution: If the allergen is removed or neutralized (e.g., through medication), the symptoms of the allergic reaction typically subside as the histamine and other mediators are metabolized and cleared from the body.

9. Desensitization: Over time, some individuals may develop tolerance or reduced sensitivity to an allergen through a process called desensitization. This involves gradually exposing the body to small amounts of the allergen over time, allowing the immune system to adapt and reduce its response.

10. Sensitization: On the other hand, repeated exposure to an allergen can also cause increased sensitivity over time, leading to more severe allergic reactions.

11. Treatment: Treatment options for allergic reactions range from over-the-counter antihistamines and nasal sprays to adrenaline (epinephrine) auto-injectors (EpiPens) in severe cases. Consulting with an allergist or healthcare provider can help determine the appropriate management and treatment strategies based on the specific allergy.

Remember that the intensity and symptoms of allergic reactions can vary from person to person and can range from mild to severe. If you experience severe symptoms or suspect anaphylaxis, seek immediate medical care.