Classifying Asthma
Over the years, there have been several ways of classifying asthma and of distinguishing one form of the disease from another.
Traditionally, doctors have divided asthma into two general categories,
Extrinsic (allergic) asthma and
Intrinsic (non-allergic) asthma, depending upon the types of stimuli that trigger attacks.
As well as these
classifications, asthma is further split up into categories such as Exercise Induced or Nocturnal.
Extrinsic Asthma
An "allergen" or an "antigen" is a foreign particle which enters the body. Our immune system over-reacts to these often harmless items, forming "antibodies" which are normally used to attack viruses or bacteria. Mast cells release these antibodies as well as other chemicals to defend the body.
Extrinsic asthma is caused by this type of immune system response to inhaled allergens such as pollen, animal dander or dust mite particles.
It was found early this century that some asthmatics had an immediate skin reaction such as swelling or redness, when an allergen was injected just under the skin. This reaction is described as "Atopic" and so Extrinsic asthma is also called Atopic or "Allergic" asthma.
People with allergic asthma and their families frequently have other allergy-related problems such as hay fever, rhinitis, skin rashes, hives, eczema and so on. Our
trigger subsectiondiscusses in detail about allergens.
Allergic asthma usually responds quite well to the use of inhaled steroids as these suppress the immune system, particularly in the lungs where the reaction is creating havoc.
Intrinsic Asthma
Intrinsic asthma is not allergy-related, in fact it is caused by anything except an allergy. It may be caused by inhalation of chemicals such as cigarette smoke or cleaning agents, taking aspirin, a chest infection, stress, laughter, exercise, cold air, food preservatives or a myriad of other factors.
Antibodies are not produced and even when skin tested to various antigens shows a reaction, these substances do not lead to an asthma attack. The cause may be an irritation to the nerves or muscles in the airways. Asthmatics' airways are unusually sensitive or "hyper-reactive" and the asthma presents itself in the usual manner of constricted smooth muscle, airway inflammation and increased mucus production.
Treatment of intrinsic asthma is not easy as it may not be known what triggers the asthma in the first place and therefore avoiding triggers can be impossible.
Avoidance of things with strong odours such as perfume or cleaning agents may be possible at home. Not going to smoky bars or discos, avoiding air which is hot/cold/humid/dry - depending on your particular trigger and keeping calm can only be maintained up to a point.
Mixed Asthma
As its name suggests, mixed asthma is a mixture of intrinsic and extrinsic asthma. These people react to some allergies but their asthma is also triggered by other things.
Is It Important To Know Which Form of Asthma I Have?
These classifications can be useful for you in understanding your disease and suggesting a path for treatment. For example, in asthma, empahasis on avoidance of known allergens can be useful.
However, you should be aware that most asthmatics have mixed asthma. For example, it is common for someone with the extrinsic form of asthma to experience attacks when he has a chest infection - an intrinsic trigger.
Approximately half of all asthmatics are triggered by allergies and the other half are not. However extrinsic asthma seems to be more prevalent in the young:
Infants or very small children have a high response to food allergies which produce wheeziness but this response becomes much less by the time the child is about ten years of age.
From about four years old children develop allergies to inhaled substances and this is more likely to stay with the person for a lifetime though it subsides during adulthood.
After young adulthood the reaction to allergies dies down and so often does the asthmatic response. These factors help to perpetuate the myth that "he will probably grow out of it" at seven, fourteen or twenty-one years old.
As well as intrinsic, extrinsic and mixed, asthma has been further categorised into other types such as Nocturnal and Exercise Induced. Your condition may have been given one of the following labels:
Nocturnal Asthma
Noctural asthma classifies asthma which suddenly worsens in the middle of the night, typically between 2 and 4am.
With nocturnal asthma, asthmatics often fall asleep quickly because they are physically exhausted only to wake some three to four hours later with breathing difficulties. They cough and wheeze, take reliever medication, a visit to the bathroom or a drink of water and try to go back to sleep. This is difficult and when the person finally sinks into a deep sleep he is woken a short time later by the alarm. He staggers out of bed feeling as if he would like to climb back into it, unfortunately it is time to get ready for work.
This type of asthmatic frequently feels totally exhausted during the day and needs catnaps to keep functioning at an adequate level. Nocturnal asthma should be taken seriously as there is a high frequency of respiratory arrest and death due to asthma in the early hours of the morning.
Bronchial Asthma
Bronchial asthma is usually an allergic reaction with breathing difficulties and wheezing. The smooth muscles wrapped around the airways spasm causing them to narrow and mucus is usually produced because the airways become irritated. Most attacks are caused by hyper-sensitivity to air-borne particles or allergies to foods.
Exercise Induced Asthma
Exercise Induced Asthma (EIA) is noticed during or shortly after exercise. The person feels wheezy and short of breath. Exercising in the winter seems to be particularly bad for this type of asthma.
Because exercise becomes a problem and is unpleasant, often the person does less exercise, becoming less fit as a result. Sometimes this deteriorates to the point where the only exercise taken is from the house to the bus stop. If you have the misfortune to be late for the bus then it becomes a major problem! Find out more about
reducing EIA.
Occupational Asthma
Industrial or Occupational asthma develops anywhere from a few months to years after starting a new job. Symptoms usually improve while on holiday or after leaving the position. Some common causes of Industrial asthma are: sawdust, chemical fumes, constant dusty conditions, close contact with animals, glue fumes, fluff off fruit, leaves etc. Read more about
Occupational Asthma.
Seasonal Asthma
Seasonal asthma can be triggered by trees, grasses or flowers releasing pollen to the atmosphere or by a particular climate. For example, some people find the summer heat makes their asthma worse, while others find spring is paricularly bad with the icrease in flowering plants.
Silent Asthma
Asthma attacks which give very little or no prior warning and very little wheezing. They are usually severe and can be life-threatening.
Cough Variant Asthma
Asthma is displayed by a persistant and irritating cough.
