Asthma and allergic diseases have increased dramatically over recent years. Australia has the second highest prevalence of asthma in the world; 1 in 4 children, 1 in 7 teenagers and 1 in 10 adults. The reasons for this are unclear. However, we do know that:

• around 4 in 10 Australians have allergic disease
• more than 8 in 10 Australians with asthma have positive allergy test results.

What is allergy?

Allergy occurs when a person’s immune system reacts to substances in the environment that do not bother most people. These substances are known as allergens and are found in house dust mites, pets, pollen, moulds and foods.

Atopy is the genetic tendency to develop allergic diseases. People with atopy are said to be atopic.

When atopic people are exposed to allergens they can develop an immune reaction that leads to allergic inflammation (redness and swelling).

This can then cause symptoms in the:

• nose and/or eyes – allergic rhinitis/conjunctivitis (hay fever)
• skin – eczema, hives
• lungs – asthma (Figure 1).

What is asthma?

Asthma is a reversible narrowing of the airways in the lungs.

Figure 1  Inflammation in asthma

Asthma symptoms include wheezing, coughing (particularly at night), chest tightness, difficulty in breathing and shortness of breath.

Asthma is a treatable health condition. Although at present there is no cure, with good management, people with asthma can lead normal, active lives.

What role does allergy play in your asthma?

Most people with asthma are atopic (see atopy). If you are atopic, allergens may be important trigger factors that can worsen your asthma.

For example, you may wheeze when you:

• vacuum or dust, as this causes house dust mite allergens to become airborne
• visit a house where a cat lives
• are outdoors in late spring and early summer, when there are high levels of pollen in the air.

There is a close link between asthma and allergic rhinitis/conjunctivitis (hay fever). If your hay fever is poorly controlled it can be more difficult to manage your asthma.

Occupational asthma is often caused by reactions to allergens in the workplace. Examples include:

• health care workers allergic to latex
• laboratory workers allergic to rats and mice
• bakers allergic to flour dust.

Content Updated March 2005