Main Causes of Asthma

Causes of Asthma

It has been estimated that there are about 300 million people affected by asthma all over the world. Among the big numbers, about 22 million are in the USA. People ranging from all ages may have asthma, but this disease usually starts during childhood. Today, there are nearly 6 million children who are suffering from asthma in the United States. And asthma causes approximately 255,000 deaths each year in the world.

asthma causes

For most children, asthma has become one of the most commonly chronic diseases, particularly for those who were born with low birth weight, who are often exposed to cigarette smoke or brought up in low level economic environment. Generally, asthma symptoms will first occur in children for the first time at approximately age of five.  Symptoms often start with frequent episodes of wheezing, together with respiratory infections. In addition, there are other factors that can also pose risks to children, such as allergies, eczema caused by allergens, or hereditary problems.

During childhood, boys have higher risks of developing asthma than girls. However, this tendency is reversed when they enter adulthood. According to researchers’ hypotheses, the size of a male’s airway is relatively smaller than that of female, which may cause this difference between boys and girls. And once it’s infected through viruses, the smaller airways of male may cause wheezing to occur more often.


Almost all asthma patients suffer from allergies. And more than 25% of patients with allergic rhinitis can develop asthma. What’s more, antibodies in the blood can lead to allergic reactions, which further inflame airways. This may be a major cause of asthma. Indoor allergens can be easily formed or dispersed. Pet dander, animal proteins, house dust mites, fungi, cockroaches, all of these can be commonly found indoors. The trend to build energy-efficient houses can also escalate the exposure to causes of asthma.

Cigarette smoke

Cigarette smoke is not only highly associated with incidences of asthma, but it also increases death rates caused by wheezing, respiratory infections and asthma. What’s worse, children whose mothers smoke, adolescents who have already begun smoking or people who are often exposed to second hand smoke, are all at a higher risk of developing asthma.

Environmental factors

causes of asthma

Today, indoor air pollutants have become the main threats to human health problems. For example, mold, chemicals and toxic gases brought out by indoor air pollution often lead to allergic reactions and asthma symptoms. Actually, nitrogen oxide released by gas stoves is also a big cause of asthma. People who often use gas stoves to cook are also at a higher risk of developing asthmatic symptoms (such as wheezing, hay fever, breathing difficulties and asthma attacks).

It has been shown that nitrogen oxide, sulfur dioxide, ozone, air pollution and cold temperatures can trigger asthma among certain people. If air pollutants are intensive, asthma symptoms can be aggravated. That’s why there are so many hospital admissions during certain times of the year. Some destructive pollutants, such as ozone gases (often released by smoke) can cause coughing, short breath or chest pain. And smoggy weather condition can also release tons of sulfur dioxide into the air, which can constrict people’s airways and further cause asthma attacks.

Another important environmental factor that causes asthma, is changes in the weather. It’s well known that cold air temperatures can cause airway constriction, congestion, secretions, or decrease mucociliary clearance. And in addition, humidity plays an important role in affecting certain population groups’ health.


Compared adults who have normal body mass indexes (BMIs), obese adults whose BMIs range from 25 to 30, have a 38% higher risk of developing asthma. Adults with a BMI of 30 or above have twice as many chances of developing asthma. Researchers say that people with non-allergic asthma, also face higher risks than people who have allergic asthma.


How you come into the world may have a great impact on your sensitivity to asthma. Usually, babies who are born by Cesarean sections may be at about 20% higher risk of asthma prevalence, than those who are born via vaginal birth. During Cesarean sections, the immune system may become infected due to bacterial exposure, a huge reason why the way you are the way you are born can impact asthmatic tendencies. If pregnant women smoke, their babies are more likely to have lower pulmonary function after birth, which can also pose the risk of asthma. According to researchers, premature birth can pose potential risks for developing asthma too.


People who often undergo stress have more chances of developing asthma, which can be partially because stress often can induce asthma-related activities, like smoking. But researchers have shown that stress is also able to modify the immune system.


causes of asthma

It has been shown that about 100 genes are associated with asthma. And 25 of them are linked to separate populations as of 2005. Genes related to asthma have an important role to play in the inflammation and management of the immune system. And although there isn’t any consistent research into studying the genetics of asthma across all population groups, further investigations should be taken to explore the relationship between asthma and complex interactions.

60% of asthma is believed to be hereditary, so a mother and father may be responsible passing on asthma to their children. According to the Centers for Diseases Control in the United States, if one of a child’s parents has asthma, the chances of him to having it too are increased and even 3 to 6 times higher, than those whose parents don’t have asthma.

What’s more, genetics may interact with environmental conditions. For instance, the genetic trait CD14 can have a gene-environmental interaction when people are exposed to the bacterial product endotoxin, which has great associations with asthma development.

Airway hyperactivity

Although researchers haven’t found clear evidences of the relationship between airway hyperactivity and asthma, cold air or allergens can probably trigger airway hyperactivity, which may cause airway inflammation. Some people may simply be at higher risk of developing asthma, while others don’t, despite having hyper reactive airways.


Atopy is a major cause of asthma. Atopy is a predisposition towards developing certain allergic hypersensitivity reactions, such as allergic rhinitis (hay fever), atopic dermatitis (eczema), allergic conjunctivitis.

Studies show that 40% to 50% of children who have atopic dermatitis, are also at risk for asthma. And they are also more likely to have more persistent and severe asthma than other adults too.

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