Is asthma hereditary?

What causes asthma?

Asthma is caused by a combination of a genetic predisposition to allergy (also called "atopy") and certain environmental factors. External factors such as household allergens (house dust, pet hair, dust mites, moulds), or pollens can trigger an allergic reaction in people with a predisposition to asthma.  

Other environmental factors can trigger asthma symptoms: 

• Tobacco smoke, including second-hand smoke
• Air pollution
• Chemical irritants such as certain cleaning and cosmetic products
• Rapid changes in weather (cold and/or dry air)
• Respiratory infections (especially viral infections)
• Emotional stress
• Physical exercise
• Hormones (in certain cases, such as in premenstrual asthma)

Asthma is also observed to be unstable in patients with allergic rhinitis (also known as hay fever). This is due to the continuity between the mucous membranes of the nose and the bronchi. This means that when an allergen comes into contact with one of these mucous membranes, it causes the same type of inflammation in the other.  

Can asthma be hereditary? 

Although heredity is a factor in the development of asthma, the disease is not systematically passed on from parent to children. 

Allergy (also called atopy), however, is a major risk factor for childhood asthma and is hereditary. A child's risk of developing allergies can be assessed based on family health history. For example, if only one parent has allergies, the risk of the child developing allergies is 20-30%. If both parents have allergies, the risk is 40-60%. 

To limit the number of risk factors triggering the development of allergies in children, there are a number of preventative measures parents can take:

• Do not smoke during pregnancy
• In pregnant women with asthma or allergies, the consumption of allergenic foods (foods that cause or are more likely to cause allergic reactions), such as peanuts, is not recommended
• It is recommended to breastfeed the child as long as possible. According to researchers, prolonged breastfeeding for more than three months can prevent the development of allergies. If breastfeeding is not possible, the use of hypoallergenic milks or formula (without cow's milk protein) is recommended. 
• Don't introduce new foods into the baby's diet too quickly
• Finally, to reduce the risk of asthma developing in children, it is advisable not to smoke in their presence, to take measures against dust mites and to avoid owning pets.

What is the link between asthma and heredity? 

Studies show that there is a genetic influence on asthma. Having a parent with asthma doubles the risk of developing the disease. However, it is difficult to say that it is a hereditary disease because there is no single gene responsible. 

Since the first study on the genetics of allergy and asthma was published in 1916, a great deal of work has been done. This have led to the identification of many so-called "asthma and atopy susceptibility genes". 

Several genes have been identified as controlling both asthma and the associated allergic and bronchial hyperactivity. The genes have been located on chromosomes 5, 6, 11 and 14. However, their more precise location is still the focus of many research teams

What is the future of research into asthma heredity? 

Research into the genetic influence in the development of asthma can have several benefits. On the one hand, it will help to better understand the causes of asthma, but on the other hand, it will also help to identify new therapeutic approaches such as gene therapy. 

In addition, in the future, screening tests could be used to assess the risk of developing asthma in a predisposed individual even before the first symptoms appear.

Another advantage made possible by this research is that researchers will have an animal model of asthma and thus facilitate research into new drugs. 

All these new perspectives could revolutionise the treatment of this disease, which affects more than 8 million British people. 

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