Pet dander consists of tiny, even microscopic, flecks of skin shed by cats, dogs, and other animals with fur or feathers. It can negatively impact indoor air quality by triggering allergies and asthma symptoms, such as sneezing, coughing, and respiratory issues. Dander can linger in the air and settle on surfaces, making it hard to remove. Regular cleaning, using air purifiers, and maintaining HVAC filters can help reduce pet dander and improve indoor air quality.