Asthma is a respiratory condition in which the lung passages become hyper-responsive to different types of stimuli. As a result, the smooth muscle in the wall of the bronchial passages contracts, along with swelling of the mucus membrane lining the airways. This is accompanied by excessive mucus production. All these lead to airway narrowing, resulting in symptoms like breathlessness, wheezing while breathing, coughing and a feeling of tightness in the chest. The severity of these symptoms varies from patient to patient and from day to day.
Unlike chronic lung disease where the lung is permanently damaged, asthma is chiefly characterized by its reversibility. No matter how dangerously severe the symptoms are, in all cases, prompt and effective treatment can open the airways again normal breathing can resume.
Child holding asthma inhaler in hands. Image Credit: OnlyZoia / Shutterstock
What are the types of asthma?
Asthma occurs in different patterns. Different types of asthma are classified by their temporal pattern, or the time when attacks occur and the following forms have been identified:
Intermittent asthma
In some people episodes of asthma occur between intervening symptom-free periods. In most cases, the asthmatic symptoms resolve spontaneously. The symptom-free periods are usually quite long. In such patients viral infections of the respiratory tract such as those which cause the common cold are a common trigger of asthma symptoms. This is especially true in small children between 2-5 years of age who may get 8-12 viral colds and coughs a year. In other cases, strenuous exercise or physical activity, exposure to cold air, or certain environmental agents have been found to act as asthma triggers.
Seasonal allergic asthma
Seasonal allergic asthma has been observed in response to the seasonal release of allergens such as pollens that occur in the environment. Mold spores are another common cause of seasonal asthma. It is important to understand how your local climate and air allergen level vary from season to season to determine whether you have this type of asthma is, and to prevent it by appropriate measures.
Non-seasonal allergic asthma
Everyone with allergies do not necessarily develop asthma, neither do all asthmatics have allergies. However, allergies do intensify asthma in some cases. Thus, exposure to cold or dry air, dust, pet hair or pollen may set off an acute attack of asthma. In addition, there is another type of allergic asthma in which the asthma triggers are not related to season, but may be due to a hyper-reaction of the airway mucosa to things that are not typically allergenic. These include viruses, air pollutants or irritants like tobacco smoke or paint fumes, heavy exercise, certain chemicals in food or drugs, and changes in the weather.
Exercise-induced bronchoconstriction (EIB)
This term is used when a bout of exercise is followed by narrowing of the airways. It may be found in up to 80% of people with asthma. However, not all cases of EIB are found in asthma patients. It is thought to be caused by the dehydration and/or heating up that occurs with strenuous physical activity in a dry climate. In children with asthma it is often the first symptom to develop.
Certain irritants which are encountered during the course of various sport activities include chlorine in swimming pools, air pollutants while jogging, running or cycling, cold dry air during winter sports, and strong smells due to chemicals or perfumes in a gym environment. The transient and treatable nature of EIB, means that patients with this condition should not be prevented from physical activity at any level whatsoever, provided it is properly managed.
Exercise-induced bronchoconstriction (EIB). Image Credit: Lopolo / Shutterstock
Occupational asthma
In this form the symptoms are caused or worsened by chemical irritants or dust in the air. Pre-existing asthma can also become worse with such exposure. Clues to the nature of a patient’s asthma may include the time of earliest symptoms coinciding with a change of workplace or job, an improvement in symptoms upon leaving the workplace, and the occurrence of breathing difficulty due to workplace chemicals. There are over 250 occupational asthma triggers or promoters. As always, pre-existing asthma also increases the risk of this condition, as does smoking and the presence of allergies in the individual or the family. Some high-risk occupations include bakers, manufacturers of drugs and detergents, those who measure grain, metal workers and laboratory workers, plastic workers and woodworkers.
Chronic asthma
Also called persistent asthma, this condition is defined by daily symptoms or those which recur several times a week. The intensity of symptoms may be quite variable, but there are no long periods without symptoms. Acute exacerbations may supervene at any time upon the chronic course of the disease. These may be traced in some cases to seasonal increase in air allergens or viral pathogens that provoke airway inflammation. Chronic asthma must be correctly identified in a patient to ensure proper intervention strategies.
Adult-onset asthma
Most cases of asthma begin in childhood, but in some patients, the first symptoms appear only in adult life. The causes may be many. Some people were just not exposed to potential triggers for their asthma until they became adults. For example, they are exposed to a house pet when their room-mate brings one home, or they begin to work in an environment containing chemical fumes, that triggers their latent hypersensitivity. It could even be a viral infection that sets off an asthmatic reaction for the first time in adulthood.
Further Reading
Mature gut microbiota in early infancy may protect against wheezing and allergies