The 'allergic march'

SINGAPORE - When a child starts to show signs of having eczema, it could signal the start of a group of conditions that include asthma and allergic rhinitis.

Together, they are known as atopic conditions.

Overseas studies show about 50 per cent of children with eczema will develop asthma subsequently.

The more severe the eczema, the higher the risk.

Children with severe eczema and severe allergies have a 70 to 80 per cent risk of developing asthma compared with 20 to 30 per cent of those with mild eczema and about 8 per cent in the general population.

This process is called the "allergic march", said Professor Hugo Van Bever, senior consultant in the division of paediatric allergy, immunology and rheumatology at National University Hospital.

Such a progression of atopic disorders is caused by a hereditary predisposition towards developing hypersensitive reactions to specific antigens.

A Singapore study published in the British Journal Of Dermatology in 2002 showed three in 10 children with eczema also had allergic rhinitis, one in 10 also had asthma and two or three in 10 had both asthma and allergic rhinitis.

The study covered 12,323 students of ages seven, 12 and 16.

About 20 per cent reported having eczema.

Common aggravating factors reported included exercise, heat and sweating, grass intolerance, thick clothing and stress.

Prof Van Bever said doctors still do not know the exact mechanisms of the "allergic march".

"But we assume it has to do with the time needed to sensitise yourself to allergens," he said.

Allergy to food, such as cow's milk and egg, can occur in infants within a few weeks to months, while sensitisation to the house dust mite takes more time - on average two or three years.

Eczema is associated more with food allergies, and asthma with the house dust mite.

What doctors agree on is that the incidence of atopic conditions is rising.

The International Study of Asthma and Allergies in Childhood (Issac) questionnaire surveys found that the cases of allergic rhinitis in six- to seven-year-olds in Singapore rose from 6.3 per cent in 1994, to 8.3 per cent in 2001 and 8.7 per cent in 2003.

The surveys also noted that the cases of eczema in six- to seven-year-olds in Singapore rose from 2.8 per cent to 8.9 per cent from 1994 to 2001.

Doctors said the number of asthma cases has been rising and may have reached its peak at around 20 per cent.

But getting to the bottom of the "allergic march" is no simple matter.

Dr Madeline Ho, consultant dermatologist at the National Skin Centre, said the risk of developing all atopic diseases is complex.

The sequential pattern described in the allergic march may not be a simple progression, she said.

The development of these diseases is strongly influenced by both genetic and environmental factors.

Some postulate a "hygiene hypothesis", which says a lack of exposure to infectious agents in childhood results in the immune system not developing properly.

Bacteria are needed to stimulate "good" immune responses.

"We believe this is also the case in Singapore where allergies are high and Singapore is a very clean country," said Prof Bever.

Dr Pang Shiu Ming, director and senior consultant of the dermatology unit at the Singapore General Hospital, added that caution should prevail in the prescribing of antibiotics early in life, especially in children with a family history of eczema.

It has never been shown that getting eczema under control early lessens the chances of the patient developing asthma and allergic rhinitis.

This is mainly because exposure to allergens cannot be avoided, said Prof Bever.

Still, Dr Chris Foo, a consultant dermatologist at Raffles Skin & Aesthetics Centre, said he would advocate getting eczema under control early, regardless of whether it reduces the chances of developing asthma or hay fever.

"Early treatment spares the child a great deal of discomfort and avoids the complications of untreated eczema, which include secondary infections and scarring from scratching, especially if eczema is severe," he said.

While there is still no cure for eczema, doctors say there are many natural options that can help the eczema sufferer manage and reduce the severity of the condition.

You can find out more about eczema at the I CAN (The Children's Asthma and Allergy Network) public symposium.

Paediatricians from National University Hospital will advise parents and teachers on how to manage allergies and asthma in school.

They will also highlight the link between asthma and sports, and the impact of eczema and allergic rhinitis on children.

wanching@sph.com.sg


Get a copy of Mind Your Body, The Straits Times or go to straitstimes.com for more stories.

VIDEOS TO WATCH

SERVICES