Final answer:
Even trace amounts of an allergen can cause a reaction in a person.
Step-by-step explanation:
True
In an allergy, a person's immune system reacts to a harmless protein from the environment, which causes unpleasant symptoms. Even trace amounts of an allergen can trigger a reaction in a person. For example, some individuals may develop watery, itchy eyes, swollen tissues, and sneezing in response to allergens like plant pollen or peanuts.