Asthma Causes

The exact cause of asthma is not known.

• What all people with asthma have in common is chronic airway inflammation and excessive airway sensitivity to various triggers.
• Research has focused on why some people develop asthma while others do not.
• Some people are born with the tendency to have asthma, while others are not. Scientists are trying to find the genes that cause this tendency.
• The environment you live in and the way you live partly determine whether you have asthma attacks.

An asthma attack is a reaction to a trigger. It is similar in many ways to an allergic reaction.

• An allergic reaction is a response by the body's immune system to an "invader."
• When the cells of the immune system sense an invader, they set off a series of reactions that help fight off the invader.
• It is this series of reactions that causes the production of mucus and bronchospasms. These responses cause the symptoms of an asthma attack.
• In asthma, the "invaders" are the triggers listed below. Triggers vary among individuals.
• Because asthma is a type of allergic reaction, it is sometimes called reactive airway disease.

Each person with asthma has his or her own unique set of triggers. Most triggers cause attacks in some people with asthma and not in others. Common triggers of asthma attacks are the following:

• exposure to tobacco or wood smoke,
• breathing polluted air,
• inhaling other respiratory irritants such as perfumes or cleaning products,
• exposure to airway irritants at the workplace,
• breathing in allergy-causing substances (allergens) such as molds, dust, or animal dander,
• an upper respiratory infection, such as a cold, flu, sinusitis, or bronchitis,
• exposure to cold, dry weather,
• emotional excitement or stress,
• physical exertion or exercise,
• reflux of stomach acid known as gastroesophageal reflux disease, or GERD,
• sulfites, an additive to some foods and wine, and
• menstruation: In some, not all, women, asthma symptoms are closely tied to the menstrual cycle.

Risk factors for developing asthma:

• hay fever (allergic rhinitis) and other allergies -- this is the single biggest risk factor;
• eczema: another type of allergy affecting the skin; and
• genetic predisposition: a parent, brother, or sister also has asthma.

Common Symptoms of Asthma

Common symptoms of asthma include wheezing, shortness of breath, chest tightness and coughing. Symptoms are often worse at night or in the early morning, or in response to exercise or cold air. Some people with asthma only rarely experience symptoms, usually in response to triggers, whereas other may have marked persistent airflow obstruction.

Asthma

Asthma is clinically classified according to the frequency of symptoms, forced expiratory volume in 1 second, and peak expiratory flow rate. Asthma may also be classified as atopic (extrinsic) or non-atopic (intrinsic), based on whether symptoms are precipitated by allergens (atopic) or not (non-atopic).

While asthma is classified based on severity, at the moment there is no clear method for classifying different subgroups of asthma beyond this system. Within the classifications described above, although the cases of asthma respond to the same treatment differs, thus it is clear that the cases within a classification have significant differences. Finding ways to identify subgroups that respond well to different types of treatments is a current critical goal of asthma research.

Although asthma is a chronic obstructive condition, it is not considered as a part of chronic obstructive pulmonary disease as this term refers specifically to combinations of disease that are irreversible such as bronchiectasis, chronic bronchitis, and emphysema. Unlike these diseases, the airway obstruction in asthma is usually reversible; however, if left untreated, the chronic inflammation of the lungs during asthma can become irreversible obstruction due to airway remodeling. In contrast to emphysema, asthma affects the bronchi, not the alveoli.

Asthma attack

An acute asthma exacerbation is commonly referred to as an asthma attack. The classic symptoms are shortness of breath, wheezing, and chest tightness. While these are the primary symptoms of asthma, some people present primarily with coughing, and in severe cases, air motion may be significantly impaired such that no wheezing is heard.

Signs which occur during an asthma attack include the use of accessory muscles of respiration (sternocleidomastoid and scalene muscles of the neck), there may be a paradoxical pulse (a pulse that is weaker during inhalation and stronger during exhalation), and over-inflation of the chest. A blue color of the skin and nails may occur from lack of oxygen.

In a mild exacerbation the peak expiratory flow rate (PEFR) is ≥200 L/min or ≥50% of the predicted best. Moderate is defined as between 80 and 200 L/min or 25% and 50% of the predicted best while severe is defined as ≤ 80 L/min or ≤25% of the predicted best.

Insufficient levels of vitamin D are linked with severe asthma attacks.