Allergens are substances that can trigger an allergic reaction in some individuals. Common allergens include pollen, dust mites, pet dander, certain foods like peanuts and shellfish, and insect stings. When a person with an allergy comes into contact with an allergen, their immune system mistakenly identifies it as harmful, leading to symptoms such as sneezing, itching, or swelling. The severity of allergic reactions can vary widely among individuals. Some may experience mild symptoms, while others could face life-threatening conditions like anaphylaxis. Identifying and avoiding allergens is crucial for managing allergies and maintaining overall health.