What causes asthma?

Genes + environment: People with asthma usually are predisposed to be allergic. This is usually inherited, and so caused by your particular genes. However, this alone is not enough. There is also clearly an effect from the environment you live in. Exactly what in the environment is responsible is unknown, but is the object of much interest and research.

Also infection: While 80% of asthma patients have allergies, there are patients whose asthma starts after they had a respiratory infection. Those infections can be due to viruses such as influenza (the real flu) or certain bacteria such as mycoplasma or chlamydia. Such patients are usually older and have no history of allergy. Still, patients who already have asthma and get infected, their asthma will get worse.

Allergies: The majority of childhood asthma is caused by allergies creating inflammation in the lungs which leads to narrowing of the air tubes in the lungs and trouble breathing. Infection certainly can cause symptoms that look like asthma. In children this often occurs after illnesses like RSV, influenza, parainfluenza, and even the common cold has been shown to have this effect.

Repair defect: Although over 50% of asthma is related to allergies, allergies do not cause asthma in everyone who is allergic. The current focus is on the malfunctioning repair mechanism in the epithelium of the airways which apparently is abnormal in people suffering from asthma. Many thing can trigger the damage (diesel particles, allergens, virus) the end result is narrowing of the airways. Sounds too complex

Many: Although the exact cause(s) for asthma is being debated, about 80% of asthma especially among younger people are related to allergy. Current thinking is that a viral infection is likely the trigger for its development. More recently, an abnormal epithelium (which covers the airways) is considered a major component for the development of asthma. A detailed review is not feasible .

Asthma: Asthma is caused by reactive airways that results in excess mucous production + narrowed airways. Symptoms are usually episodic and triggered by allergies (grasses, pollen, mould) or infections. Some people get exercise-induced symptoms.

Genetics/external fr: There is ample evidence that true asthma is genetically linked to the issues of allergy & eczema & frequency is higher when one or both parents are affected. Lower respiratory tract viruses often trigger both infectious wheezing & that of true asthma early on with infectious wheezing subsiding after 3-4y. Allergies often co-exist but less than 5% of events are allergy driven alone.