Asthma, allergy rates shoot up

By REBECCA WALSH

The number of allergy and asthma sufferers is rising, but researchers are struggling to understand why.

International studies suggest the number of people suffering from allergies has doubled or tripled over the past 30 to 40 years.

Dr Rohan Ameratunga, an Auckland adult and paediatric allergist, says New Zealand studies indicate that 40 per cent or more in this country are affected by an allergy.

Asthma sufferers in New Zealand are entering hospital at more than double the rate of 30 years ago, an Asthma and Respiratory Foundation study has found.

While the cause remains unknown, allergies are considered the most common and important risk factor for the development of asthma in adults and children.

Why the increase in allergies?

One theory is the hygiene hypothesis - because children in developed countries are no longer exposed to serious infection their immune system instead generates allergies.

That theory has the support of Allergy New Zealand president Natalie Lloyd, who believes increased usage of anti-bacterial products may be adding to the problem.

"I think the theory is a little bit of old-fashioned dirt is a good thing. It sets our immune system up."

Other explanations include the rise in pet ownership.

Many people are allergic to the proteins from cat skin and saliva (dander).

Dr Ameratunga says increasing use of carpet and better insulation in houses provides perfect conditions for dust mites to multiply, further aggravating allergies such as hayfever.

Increased awareness and better detection and diagnosis of allergies by doctors are also reasons cited for the rise in allergy levels.

An international study of asthma and allergies in childhood involving New Zealand children and researchers has found major differences between countries, which are most likely explained by environmental factors, such as diet and economic development.

For example, New Zealanders tend to have a diet that is rich in meat products rather than vegetables, rice, nuts and starch, which could be contributing to asthma rates.

Dr Innes Asher, associate professor of paediatric respiratory medicine at Auckland University, says the research suggests that as countries develop and change their lifestyles, environmental factors which protect against asthma and allergic diseases are being lost.

Who is affected?

Children are more likely to develop allergies if there is a family history of them, Dr Ameratunga says.

If one parent has an allergy there is a 30 per cent chance the child will develop one. If both parents have allergies then the chances increase to 50-60 per cent and up to 80-90 per cent if an older sibling has an allergy.

The most common allergens are dust mites and grass pollens, which can trigger hay fever, asthma and eczema. Cat allergies and allergies to foods, such as peanuts, milk, eggs, wheat and soya, are also common. Some people have allergies to latex, insects or particular drugs.

An article in the New Zealand Medical Journal in March last year suggested asthma affected 25-30 per cent of the general population, hay fever 10-19 per cent and eczema about 15 per cent.

Allergy New Zealand, a voluntary organisation supported by medical specialists, estimates about 12 per cent of children have food allergies.

Mrs Lloyd says most children will outgrow them, particularly if their exposure is limited. For example about 80 per cent of children with a cow's milk allergy outgrow it by the time they are 3 or 4-years-old. But for many it is the start of what is known as the "allergic march". As they outgrow one allergy they develop another.

Mrs Lloyd says oldest siblings tend to be more prone to allergies, while younger siblings are exposed to infections brought home by their older brothers and sisters. Boys are more likely to suffer from allergies, although it is not known why.

Coping with allergies.

The key is good diagnosis and management.

When a child is first diagnosed, simple things like food shopping can be difficult. Milk products have about 20 different names and are often used in unexpected foods, for example as part of the flavour base for salt and vinegar chips.

Mrs Lloyd says new labelling laws which come into effect in May, will make it compulsory for a list of major allergens to be declared.

Though most children learn quickly about what is safe and unsafe for them, parents may be worried about a child with a serious allergy playing at their house. Kindergartens and schools are not legally required to have practices in place for children with allergies.

Mrs Lloyd says one of the biggest issues for allergy sufferers is a lack of services. Outside Auckland there are few clinics and the wait to see a specialist in Auckland ranges from 9-12 months.

Treatment is costly.

An epi-pen (adrenaline injection), which can only be used once and has a shelf life of about 13-14 months, costs up to $160.

Allergy alert

* What is an allergy?

An allergy occurs when the body's immune system overreacts to normally harmless substances, which may be in the air or water, or things we touch or eat.

* What practical things can you do to reduce the chances of your child developing allergies?

Avoid certain foods such as peanuts, nuts, fish and shellfish during pregnancy and while breastfeeding.

Breastfeed as long as possible and introduce solids as late as possible.

* Other general precautions:

Use special covers on mattresses and pillows to help to reduce problems associated with dust mites.

If you are redecorating consider wood or tile floors, instead of carpet and select fabrics that can be easily washed for curtains and furnishings.

Avoid sheepskin rugs and sheep wool fabrics for your baby.

Make sure soft toys are washable and regularly washed in hot water over 55C. You can also freeze them occasionally to eliminate dust mites and put them in the drier to warm up afterwards.

Don't get new pets, keep pets outside.

Don't smoke.

* What are the early warning signs of allergy?

Colic (not exclusively caused by allergy but can be an allergic symptom), excessive vomiting, abdominal pain, diarrhoea or constipation.

Skin rashes and eczema.

Swelling or welts.

Persistent sniffling and wheezing, permanent stuffy nose, frequent colds, recurring ear infections.

Any unexplained change of behaviour as well as difficulties in breastfeeding or refusal of food.

- Source: Allergy New Zealand and Dr Rohan Ameratunga, adult and paediatric allergist.

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