What happens to our body when we have Immune Response : 1. Sensitization Phase 1) Initial exposure: When you first encounter an allergen (e.g., pollen, pet dander, or food), your immune system mistakenly labels it as harmful. 2) Production of antibodies: The immune system produces Immunoglobulin E (IgE) antibodies specific to that allergen. These antibodies attach to immune cells called mast cells and basophils, which are found in tissues and the bloodstream. 2. Subsequent Exposure 1) Allergen recognition: The next time you're exposed to the same allergen, it binds to the IgE antibodies on mast cells and basophils. 2) Chemical release: This triggers the release of inflammatory chemicals like histamine, prostaglandins, and leukotrienes from these cells. 3. Inflammatory Response Histamine's role: Histamine is a major player in allergic reactions. It causes: > Swelling and inflammation by increasing blood flow to the affected area. > Itching by irritating nerve endings. > Sneezing, nasal congestion, and runny nose by stimulating mucus production. Other symptoms: Chemicals like leukotrienes and prostaglandins exacerbate the reaction, causing symptoms such as hives, watery eyes, and difficulty breathing.