What Is The Relationship Between Allergy And Asthma?

Allergy and asthma are two separate medical conditions, despite the fact that asthma often co-exists with a diagnosis of allergy, especially in children and in teenagers.

The development of asthma reflects a particular genetic or innate predisposition  to the disease. In addition, environmental influences have been recognized as  significant in the emergence of clinical asthma.

The precise interplay between  environmental and hereditary factors leading to asthma is still insufficiently  understood. It has long been noted that some environmental exposures  are associated with progression to asthma while other types of exposures might  possibly prevent or delay the development of asthma in susceptible persons. The  complex relationships are the subject of ongoing research, at the molecular level,  in laboratory animals, and in human populations.

Indoor environments play a greater role than outdoor ones in terms of asthma  development. The 2000 report on: Clearing the Air: Asthma and Indoor Air Exposures from the  Institute of Medicine concludes that there is sufficient evidence to support a causal  relationship between asthma development and exposures to dust mites (increased  risk of asthma) and environmental tobacco (probably increased risk). Cockroaches,  cats, and dogs carry a “maybe” increased risk.

Allergy involves our immune systems, which play an important role in asthma as well. An allergy is a very specialized immune response to a specific agent, called an allergen. Examples of allergens include a variety of agents, such as cat dander, cockroach, mold, peanut, penicillin, and ragweed to mention just a few. Most people can play with a cat or eat peanuts, take penicillin for a strep throat infection, or inhale ragweed in late summer in the Northeast and suffer no ill effects at all. That is because they are not allergic to any of those allergens. Exposure to an allergen is harmless to a person who is not allergic to that particular allergen. The per-son who is allergic to cats or to peanuts, on the other hand, will, upon exposure to cats or peanuts, develop one or more allergy symptoms. Allergy symptoms may arise from different body organs, including the skin (hives), membranes of the eye (conjunctivitis) and nose (rhinitis), the intestines (cramping, nausea, vomiting, diarrhea), as well as the lungs (wheeze). Asthma, a word derived from the Greek for hard breathing ( ) is, as mentioned in Question 1, a disease whose target organ is the lung.

A person with asthma may experience intermittent and varying symptoms of cough, mucus production, wheeze, and breathlessness. Part of modern asthma management includes identifica-tion of an individual’s asthma symptom triggers, with consequent trigger avoidance to any degree possible. A trigger is a stimulus to the development of asthma symptoms, as explained in more detail in Question 41. Some triggers will provoke asthma symptoms in most persons with asthma and are considered universal, whereas other triggers are more personal or idiosyncratic. Cold air and respiratory infections are two examples of universal asthma triggers.

That means that the majority of persons with asthma, if exposed to very cold air for  a long enoug period of time, will likely notice the emergence of some asthma symptoms. They might, when suffering from a significant respiratory infection, also start to develop increased cough and wheezing at night, for instance. Now, take those persons with asthma and expose them to a cat or to ragweed. Those who have no allergy to either cat or ragweed will have no respiratory symptoms at all, whereas those persons with asthma who also hap-pen to be allergic to cats or ragweed, will, if the exposure is of sufficient magnitude, develop allergic symptoms.

They may first notice itchy eyes, followed by a runny nose and perhaps wheezing and some cough. The allergen is not a cause of asthma, but rather a trigger (allergic trigger) for the development of asthmatic symptomatol-ogy. Exposure to known allergens in a person with both asthma and an allergy can be a symptom trigger for his or her asthma. Although asthma is different from allergy, a dual diagnosis is far from unusual, especially in children and in adolescents. Published studies indicate that between 60% and 80% of children with asthma also have allergies. An individual of any age with significant allergies is more likely to carry a diagnosis of asthma as compared to some-one without any allergy at all. A 12-year-old boy who has been allergic to peanuts or fish since he was a toddler, for example, does not automatically also have asthma.

An adult who is allergic to sulfa antibiotics similarly does not inevitably carry an asthma diagnosis. Consider on the other hand, a 17-year-old girl with asthma and an allergy to tree pollen. Each spring, as tree pollen counts rise, she experiences cough, abnormal sensations of chest tightness, and wheezing that requires her increasing and adjusting her inhaled asthma medications. Both the boy and the adult have allergy, and yet they do not have asthma. They each have a diagnosis of allergy alone, whereas the 17-year-old carries a dual diagnosis of asthma with allergy, with a specific allergen (tree pollen) acting as one of her identified asthma triggers.

Her asthma is not caused by her allergy but her asthma symptoms are clearly triggered and exacerbated each spring by her exposure to tree pollens.

Kerrin’s comment:

My son developed eczema as an infant. It was particularly bad on his face, and he would develop patches that would not heal no matter what we treated them with, until we finally had to use a steroid cream. He would also occasionally develop hives after breastfeeding, and at 6 months I finally had to wean him because I was down to eating almost nothing for fear that I would induce an allergic reaction, because we could never quite pinpoint exactly what he was allergic to. His eczema eventually went away, but it was replaced with asthma. I was told that it is not unusual for young children with eczema to later develop asthma.