Allergens cause allergic reactions by triggering an immune system response in people who are sensitive to them. When an allergen enters the body, the immune system mistakenly identifies it as harmful and reacts by releasing chemicals like histamine. This immune reaction can inflame the skin, sinuses, airways, or digestive system, leading to various symptoms

. The effects of allergens can range from mild to severe and include:

• Sneezing, runny or stuffy nose, itchy and watery eyes (allergic rhinitis or hay fever)

• Skin reactions such as rashes, hives, eczema flare-ups, redness, and itching

• Respiratory symptoms like coughing, wheezing, shortness of breath, and asthma attacks

• Gastrointestinal symptoms including abdominal pain, vomiting, diarrhea

• Severe systemic reactions called anaphylaxis, which can be life-threatening and involve swelling, difficulty breathing, low blood pressure, and even loss of consciousness

Common allergens include pollen, pet dander, dust mites, certain foods (e.g., peanuts, shellfish), insect stings, medications, mold, and latex

. In summary, allergens cause allergic reactions by provoking an overactive immune response that leads to inflammation and a variety of symptoms affecting the skin, respiratory tract, digestive system, and sometimes the whole body in severe cases