Allergenic substances are materials that can trigger an allergic reaction in sensitive individuals. Common examples include pollen, dust mites, pet dander, and certain foods like peanuts and shellfish. When a person with a sensitivity comes into contact with these substances, their immune system mistakenly identifies them as harmful, leading to symptoms such as sneezing, itching, or swelling. These reactions can vary in severity, from mild discomfort to life-threatening conditions like anaphylaxis. Understanding allergenic substances is crucial for managing allergies and preventing exposure. Individuals with known allergies often carry medications, such as epinephrine, to treat severe reactions quickly.