You may have noticed that allergies and asthma often go hand in hand. Roughly, 70% of children with asthma have some type of allergy. So do allergies cause asthma? Or does asthma cause allergies? The answer to both questions is no; one does not cause the other but the two conditions do have a strong connection.
Inflammation & Your Immune System
Allergies and asthma are both inflammatory conditions caused by dysfunction of the immune system. Sometimes they are referred to as “atopic diseases”. The immune system is the body’s defense to foreign invaders, such as bacteria, viruses, pathogens, fungi, etc. When the immune system detects these foreign invaders, it releases cells that seek out and destroy them. Inflammation is one of the first responses of the immune system to infection. Usually, the immune system keeps us healthy; however, a malfunctioning immune system can lead to illness. This is what happens with allergies and asthma.
Asthma vs. Allergies
With allergies, the immune system is hyperactive and produces an unnecessary inflammatory response to a traditionally harmless substance (such as a food protein). Asthma is a chronic lung disease characterized by episodes of inflammation and narrowing of the airway in response to certain "triggers." These triggers vary from patient to patient and may include infectious agents, exercise, stress, pollutants such as cigarette smoke, and common allergens such as cat dander, dust mites, and pollen.
Is there a link?
There are approximately 9 million kids in the US who have asthma. Of this 9 million, about ¾ have asthma that is triggered by allergies. Remember, we talked about different triggers for asthma symptoms (exercise, pollen, allergens, etc.). Patients whose asthma is triggered by allergens are often said to have “allergic asthma”.  According to the Asthma and Allergy Foundation of America, allergic asthma is the most common type of asthma, affecting around half of asthma patients.
Does Genetics Play a Role?
Atopy refers to the genetic tendency to develop allergic diseases, such as eczema, allergies and asthma. Someone with “atopy” produces certain antibodies associated with allergic disease. Genetics and environmental factors both contribute to whether a patient does or doesn’t develop atopic diseases. Not all people with atopy (that genetic predisposition) go on to develop allergic diseases because environmental factors play a role too; However, they are significantly more likely to. Likewise, not all people with atopic disease have atopy (but most do).
Genetics obviously plays a big role in the development of allergic diseases. If one parent has an atopic condition, their child has a 1 in 4 chance of having some form of atopic disease (not necessarily the same one as the parent). If both parents have an atopic condition, the child is more than 50% likely to develop an atopic disease.
Hopefully, this information gives you a better understanding of why asthma and allergies are so often seen together. While neither one causes the other, some people have a genetic predisposition which puts them at a greater risk for developing all forms of allergic disease (such as allergy, eczema and asthma). So if you have one allergic disease, you have a higher risk for developing other types of allergic conditions in comparison to the general population.
Have you found this to be true with your little ones? Be sure to share your experiences with us in the comments!
 World Health Organization. Global surveillance, prevention and control of chronic respiratory disease: a comprehensive approach, 2007.
 The Nemours Foundation/KidsHealth®© 1995- 2010. http://kidshealth.org/.
 American Academy of Allergy Asthma & Immunology.
 Atopic Diseases in Childhood. Gold MS and Kemp AS. MJA 2005; 182 (6):298-304.  The National Eczema Association. http://www.nationaleczema.org/.