What causes asthma?

We also call asthma bronchial asthma. The occurrence of asthma brings great physical harm to patients, so we must do a good job in preventing asthma. We also need to understand some knowledge about asthma so that we will not be at a loss when an asthma attack occurs. There are many causes of asthma. As long as we know the causes of asthma, we can try to avoid the causes of asthma to prevent asthma.

There are many factors that lead to asthma, such as genetic factors, infection, climate change, environmental pollution, smoking and exercise. Let’s take a look at the causes of asthma below.

It is currently believed that bronchial asthma is a multi-gene hereditary disease with a clear tendency to familial clustering, and its occurrence is affected by both genetic and environmental factors.

1. Genetic factors

In recent years, with the development of molecular biology technology, progress has been made in the study of asthma-related genes. Chromosomes 5, 6, 11, 12, 13, 14, 17, 19, and 21 may be related to asthma, but the specific relationship is not yet clear. The polygenic inheritance characteristics of asthma are: incomplete penetrance; genetic heterogeneity; polygenic inheritance; synergistic effect.

This results in a genetic linkage association being found in one population but not in a different population.

2. Allergens

(1) Allergens

Dust mites are the most common allergen and an important cause of asthma worldwide. There are four common types, namely house dust mites, dust mites, dust mites and hairy mites. House dust mites are the most important mites in persistently humid climates. Fungi are also one of the allergens present in indoor air, common ones are Penicillium, Aspergillus, Alternaria, etc. Pollen and grass pollens are the most common outdoor allergens that trigger asthma attacks. Woody plants (tree pollen) often cause spring asthma, while grass pollen from grasses often causes autumn asthma.

(2) Occupational allergens

Common allergens include grain powder, flour, animal fur, wood, silk, linen, kapok, feed, mushrooms, rosin, reactive dyes, ethylenediamine, etc. The mechanism of action of low molecular weight sensitizers is still unclear. High molecular weight sensitizers may sensitize patients and cause asthma attacks through the same allergic reaction mechanism as allergens.

(3) Drugs and food additives

There are two types of drug-induced asthma attacks: specific allergies and non-specific allergies. The former is most commonly caused by allergies to biological products, while the latter occurs in sympathetic blockers and agents that enhance parasympathetic nerve action. Most food allergies are type I allergies. Seafood such as milk, eggs, fish, shrimp and crab, and seasonings can act as allergens and often trigger asthma attacks in patients.

3. Precipitating factors

(1) Infectious asthma The formation and onset of asthma are related to repeated respiratory tract infections, the most common of which are rhinoviruses, followed by influenza viruses, parainfluenza viruses, respiratory syncytial viruses, and coronaviruses.

(2) Climate change: Changes in temperature, humidity, air pressure, and ions in the air can trigger asthma, so it is more common in cold winters or when the climate changes from autumn to winter.

(2) Smoking Cigarette smoke (including passive smoking) is the main source of indoor triggers and an important asthma trigger, especially for asthmatic children whose parents smoke, who often have asthma attacks due to smoking.

(3) Environmental pollution

It is closely related to the onset of asthma. Among the harmful irritants that induce asthma, the most common are coal gas (especially SO2), oil smoke, passive smoking, insecticide sprays, etc. Smoke can irritate the airways of asthma patients who are in a hyper-reactive state, causing bronchi to constrict or even spasm, leading to asthma attacks.

(4) Psychological factors: Patients’ nervousness, anxiety, and emotional agitation can also trigger asthma attacks, which are generally believed to be caused by activation of the cerebral cortex and vagus nerve or hyperventilation.

(5) Exercise

Asthma patients may suffer from asthma attacks after strenuous exercise, which are often manifested by coughing, chest tightness, wheezing, and wheezing can be heard by auscultation. Most patients can relieve themselves within an hour. Although some patients do not have asthma symptoms, exercise may induce bronchial smooth muscle spasm.

(6) Drugs: Some drugs can cause bronchial asthma attacks, mainly non-steroidal anti-inflammatory drugs including aspirin, iodinated contrast agents, or sympathetic nerve blockers.

(7) Physiological factors such as menstruation and pregnancy. Many female asthma patients experience worsening asthma symptoms 3 to 4 days before menstruation, which may be related to the sudden drop in progesterone during the premenstrual period.

(8) Perinatal fetal environment

The fetal thymus at 9 weeks of gestation can produce T lymphocytes, and the placenta mainly produces type II helper T cells (Th2) factors throughout the pregnancy. Therefore, in the lung microenvironment, Th2 reactions are dominant. If the mother already has a specific constitution and is exposed to a large number of allergens during pregnancy or is repeatedly infected with respiratory viruses, especially syncytial viruses, the allergic reactions she regulates may be aggravated, leading to the possibility of allergic reactions and asthma after birth.

Above we introduced what asthma is. We know that the occurrence of asthma brings serious physical harm to patients, so we must do a good job of preventing asthma in our daily lives. To prevent asthma, we must understand the causes of asthma. The above article introduces the causes of asthma in detail.