Final answer:
It is false that people only suffer from pet allergies when the pet is physically present; allergens such as pet dander can cause allergic reactions even without the pet's presence. Allergies involve the immune system reacting to harmless environmental proteins, which is not the same as autoimmune diseases where the immune system targets the body's own proteins.
Step-by-step explanation:
The statement that people only suffer from pet allergies when the pet is physically present is false. Pet allergies are caused by an immune system reaction to proteins found in pet dander, saliva, or urine. Even when the pet is not present, these allergens can linger in the environment on furniture, clothing, and other surfaces. Therefore, an allergic person can experience unpleasant symptoms even in the absence of the pet.
Allergies and autoimmune diseases both involve an overactive immune system, but they function differently. In an allergy, the immune system mistakenly identifies a harmless environmental protein, such as pet dander, as a threat and produces antibodies to attack it, leading to allergic reactions. However, autoimmune diseases occur when the immune system mistakenly targets and reacts to the body's own proteins.