One of the primary causes of asthma symptoms, especially in childhood asthma, are allergies. Any number of environmental triggers can play a role, including both indoor and outdoor allergens. The most common indoor allergic causes of asthma include dust mites, mold spores, cat and dog dander, and cockroach allergen. Seasonal pollens including weed, tree, and grass pollens, are the most common causes of seasonal asthma. Outdoor or indoor mold spores can contribute to year-round asthma symptoms. On rare occasions, food allergies can precipitate symptoms of asthma as well. Allergy induced asthma should certainly be suspected as the cause of asthma if symptoms appear only in the spring and fall, or when exposed to pets or dusty and moldy environments.
Recent research has shown a higher incidence of allergic asthma in urban versus rural areas. Some scientists believe the migration of people away from farms and away from the tough and dirty environment of agricultural living has left our immune systems soft and unchallenged. They hypothesize that the “allergic” side of our immune systems has been allowed to over-react since the “anti-infection” side of our immune systems no longer is called on to fight off infectious diseases such as TB and the multitude of microbes, in the form of germs and dirt associated with agricultural or rural living.
Not all asthma, however, is triggered by allergies. Approximately one half of all asthmatics have non-allergic asthma. Symptoms of the non-allergic asthmatic are not brought on by allergens, but by exposure to irritants and other non-allergic triggers. The most common asthma causes include upper respiratory viral infections (the common cold), sinus infections, and gastro-esophageal reflux. Asthma symptoms can be brought on during or after exercise or laughter, and upon exposure to cold air, cigarette smoke and other strong smells (perfumes, aerosols, cleaning products, etc.), poor air quality, and changes in the weather. Exercising in the cold can be very problematic as well.
In short, there are many different causes of asthma and its symptoms. An asthma specialist should be consulted to help to determine the specific cause of asthma symptoms for patients experiencing symptoms.