Which type of chemical can act as an allergen?

The correct choice identifies that all allergy-inducing chemicals can act as allergens. An allergen is any substance that can cause an allergic reaction, which encompasses a wide range of chemical types beyond just metals, pet dander, or floral pollen. This category includes various proteins, chemicals in food, dust mites, mold spores, and even substances used in medical and dental settings, such as latex and certain medications. Understanding that an allergen can be any chemical compound that triggers an immune response is crucial for recognizing and managing allergies in clinical and everyday contexts.