Asthma has been prevalent for thousands of years as we know of. Asthma and wheezing were considered to be acts of god to act of evil spirits in the past. Early twentieth-century studies considered this ailment as a pure psychosomatic illness. Eventually concrete research refuted these erroneous psychiatric theories and proved that it was a true physical illness with multiple causes.
One major study was done by Dr. Kevin H. Salter in 1864 to prove that asthma is a pure physical ailment. He discovered that animal dander could trigger asthma and when the subject was in an environment free of animal dander he ceased to experience conditions of this ailment.
There are many known and unknown causes for asthma. For example the disease can be inherited, but it does not always follow a predictable line of inheritance. This means that it can skip from one generation to another or surface in cousins, uncles, or aunts. Many asthmatics who lack a family background of this disease could have had grandparents or parents who had been wrongly diagnosed with say chronic bronchitis or pulmonary emphysema when they could have actually had asthma.
The presence of an asthma gene does not always mean that one will develop the disease. Many brothers and sisters of asthmatic patients carry the asthmatic gene, yet never show any outward signs of the disease.
Asthma is widely prevalent in almost all parts of the world but it is worse in some countries than in others. The disease is more prevalent in Western Europe, Great Britain, and North America, where almost 10 percent of the total population have asthma.
Asthma is more common in urban than rural areas. It is probably because of the environment urbanites may be living in. The high pollution levels in urban areas are a trigger for asthma. Lack of fresh air in indoor surroundings, food habits, stress levels all trigger asthma in much higher proportions. Indoor air pollution has more impact in triggering asthma than outdoor air pollution. Most homes and offices today are completely air-conditioned that we rarely open the window to let fresh air in.