Allergy Capital

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Asthma and Allergy:Overview

One in 10 people get asthma. People with asthma have "irritable" bronchial tubes due to inflammation. Muscle around the small and medium sized airways contracts, making it harder to breathe. Common asthma triggers include allergy, infection and smoke.

What is asthma?
One in 10 people get asthma. People with asthma have "irritable" bronchial tubes. Muscle around the small and medium sized airways contracts, making it harder to breathe. Some cough or wheeze. Others simply get puffed or feel unfit. Diagnosis is not always easy, particularly in children with occasional asthma. Lung function testing is often unreliable in young children, as "wheezes" are often absent or occasional. Other disorders such as severe hay fever or sinus infection can also cause cough or wheeze.

Smoke from bushfires can aggravate asthma (photographs taken January 2003 in Canberra ACT)

What causes asthma?

Asthma is an inflammatory condition affecting the airways. The result is "irritable" bronchial tubes that contract in response to many irritants like cold air, cigarette smoke or the smoke from bushfires. This irritability results in narrowing of the bronchial tubes and symptoms like wheeze and shortness of breath.

Most sufferers are allergic, and many already have hay fever or eczema. Like other allergies, asthma often runs in families. The major causes of airway inflammation are exposure to allergen (e.g. dust mite, animals, mold spores or pollens), cigarette smoke, smoke from bushfires and respiratory infections. This provides a rationale for recommending avoidance of these factors. When asthma is severe or regular, medicines can be used to that reduce airway inflammation. Some patients undergoing immunotherapy for their hay fever find that their asthma improves as well.

Can asthma be cured?
Some patients (particularly young children) may grow out of their symptoms with time, and others will have few symptoms if they avoid their major triggers. Many patients require some medication to remain in control of their asthma. It is important to realize that drugs do not cure asthma. Symptoms usually return when the medicines are stopped unless there has been a change in the patient's trigger factors. Moderate to severe asthma in teenagers and young adults rarely resolves completely, even if it improves. That's why it is important to take control of your asthma, and not let it dictate to you!

Allergy and asthma
Contrary to popular opinion, it is inhaled allergen (like dust mite, grass pollens and animals) rather than food that contributes to airway inflammation in asthma. Taking patients off wheat or dairy products is usually a waste of time and can adversely affect nutrition, particularly in young children.

When food allergy does occur, reactions are usually severe and dramatic and usually accompanied by rashes, throat swelling or gut upset at the same time. Nuts, fish, shellfish, milk, eggs are the most common triggers. Dietary preservatives like sodium metabisulfite (220, 221, 222) in wine, dried fruits, vinegar, grapes and some fruit salads can make some people wheeze. MSG has a bad (and often undeserved) reputation for triggering asthma. Unfortunately, allergy testing is unreliable for confirming sensitivity to these substances. Strict "elimination diets" are only occasionally useful for the management of asthma.

Other Asthma Triggers

• Infection
• Sinusitis
• Acid reflux
• Irritants like cigarette smoke or wood smoke
• Medication such as beta-blockers, aspirin and even some herbal medications can trigger severe attacks.

Measuring asthma severity
How one treats asthma depends on:

• Frequency of symptoms
• Medication use
• Exercise Tolerance
• Measurement of lung function. E.g. peak flows
• Other Measures. How much time off school or work have you lost due to asthma? How often do you wake in the morning feeling tight in the chest? How often do you get nighttime asthma?

When should regular asthma medication be considered?

• When relievers are needed more than 3-4 times per week to control spontaneous asthma
• When asthma attacks are frequent, or infrequent but life threatening
• When there is significant exercise asthma despite pre-treatment with medication
• When lung function is poor but reversible towards normal with medication

Managing acute asthma attacks
The commonest triggers of acute attacks are infection or exposure to large amounts of allergen, such as when traveling away from home. By comparison, medications and food allergy are relatively rare triggers of acute attacks. Action taken is based on a combination of the symptoms you have, the amount of medication you need and your peak flows. Because peak flows are less reliable in young children, action plans tend to be based more around symptoms in this group.

Signs of Worsening Asthma

• More frequent symptoms
• Greater need for "relievers"
• Dropping peak flows
• Greater peak flow variability
• Increased mucous production (which can occur in asthma and not just infection)

Danger Signs of Rapidly Worsening Asthma

• Symptoms get worse very quickly
• They persist even after you have taken your reliever, or rapidly return
• You are needing your reliever more than every 2-3 hours
• You have severe trouble breathing or speaking because of asthma

Options for treating worsening asthma
Your doctor will advise you as to the most appropriate approach. Advice may include:

• Using additional reliever medication
• Increasing the dose of "preventer" medication
• Starting cortisone tablets or syrup for more severe asthma until review by your usual doctor
• Seeking treatment in hospital for severe or unresponsive asthma
  
  

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References

• Johnston FH, Kavanagh AM, Bowman DM, Scott RK. Exposure to bushfire smoke and asthma: an ecological study. Med J Aust. 2002 Jun 3;176(11):535-8.
• Jalaludin B, Smith M, O'Toole B, Leeder S. Acute effects of bushfires on peak expiratory flow rates in children with
  wheeze: a time series analysis. Aust N Z J Public Health. 2000 Apr;24(2):174-7.
• Smith MA, Jalaludin B, Byles JE, Lim L, Leeder SR. Asthma presentations to emergency departments in western Sydney during the January 1994 Bushfires. Int J Epidemiol. 1996 Dec;25(6):1227-36.
• Halken S, Host A, Niklassen U, Hansen LG, Nielsen F, Pedersen S, oSterballe O, Veggerby C, Poulsen LK. Effect of mattress and pillow encasings on children with asthma and house dust mite allergy. Allergy Clin Immunol. 2003 Jan;111(1):169-176
• Mihrshahi S, Peat JK, Marks GB, Mellis CM, Tovey ER, Webb K, Britton WJ, Leeder SR. Eighteen-month outcomes of house dust mite avoidance and dietary fatty acid modification in the childhood asthma prevention study (CAPS). J Allergy Clin Immunol. 2003 Jan;111(1):162-168
• Kuo HW, Lai JS, Lee MC, Tai RC, Lee MC. Respiratory effects of air pollutants among asthmatics in central Taiwan. Arch Environ Health. 2002 May-Jun;57(3):194-200.
• Nicolai T. Pollution, environmental factors and childhood respiratory allergic disease. Toxicology. 2002 Dec 27;181-182:317-21.
• Osur SL. Viral respiratory infections in association with asthma and sinusitis: a review. Ann Allergy Asthma Immunol. 2002 Dec;89(6):553-60. Review.