Final answer:
The correct answer is allergens. Allergens are harmless antigens that cause an inflammatory response from the immune system, leading to allergic reactions. They include substances like pollen, pet hair, certain foods, and specific medications.
Step-by-step explanation:
These antigens, called allergens, include pollen, pet hair, certain foods, and some medicines, such as penicillin. The correct answer to fill in the blank is allergens. An allergy is a disease in which the immune system makes an inflammatory response to a harmless antigen. Any antigen that causes an allergy is called an allergen. Common allergens include pollen, dust mites, mold, specific foods such as peanuts, insect stings, and certain medications such as aspirin.
Allergens may be inhaled or ingested, or they may come into contact with the skin. Symptoms of a common allergy such as pollen can include sneezing, a runny nose, nasal congestion, and itchy, watery eyes. When the immune system erroneously identifies a usually harmless substance as a threat, it can trigger an allergic reaction, leading to various symptoms depending on the severity of the immune response and the type of exposure.