Exposure to pollution that is common in cities is linked to a greater risk of asthma. While you may not be able to control what’s happening externally, experts suggest reducing indoor allergens at home, as triggers like tobacco smoke, dust mites, cockroaches, and pet dander can aggravate asthma. If accessible to you, try to vacuum regularly, keep surfaces clean, close windows and doors when possible, and reduce moisture in the bathroom and kitchen areas.