Question 2 A/An is a substance that produces an allergic reaction in an individual. square A Moving to another question will save this response.

The correct answer is: allergen.<br /><br />An allergen is a substance that produces an allergic reaction in an individual. Allergens can be various substances such as pollen, dust mites, pet dander, certain foods, or insect stings. When an individual with allergies is exposed to an allergen, their immune system overreacts, leading to symptoms such as itching, sneezing, runny nose, or even severe reactions like anaphylaxis.