Childhood allergies can persist into adulthood, and certain allergic reactions can be life-threatening.

Fortunately, allergies are not common, and in Singapore no more than 5 per cent of children under the age of 12 have food allergy.

Some childhood allergies can be outgrown. Experts say that 80 per cent of children will outgrow their egg and cow's milk allergies by the time they are five years old.

Then there are non-food allergens such as animal furs.

If a child has a sneezing fit when a dog brushes past him or has a coughing fit after sipping a milkshake, he could be an allergy sufferer.

The term allergy describes the body's response to a substance known as an allergen. Milk, for instance, is not harmful to most people. But to someone allergic to it, it will provoke an immune response and a reaction that causes symptoms.

To an allergic person's immune system, an allergen is an 'invader' which requires a special type of antibody (IgE) to attack. Other blood cells join in, releasing more chemicals (including histamine). The result: allergic reaction symptoms.

These include a runny nose, itchy eyes, cough, nausea and skin rashes.

Apart from animal furs, non-food allergens also include dust mites, plant pollen, mould and insect bites.

The most common are dust mites and pollen, said Dr Stephen TS Lee, senior partner and consultant ear, nose and throat surgeon at Raffles Hospital.

Dr Lin Kai Wei, family physician with International Medical Clinic, said the more common allergic conditions that affect children are allergic rhinitis (sensitive nose), eczema (sensitive skin) and asthma (sensitive airways).

Food allergens include shellfish and peanuts. But eggs and cow's milk are the most common childhood food allergies, said Dr Lee.

'The majority of children are allergic to only one or two foods,' added Dr Anne Goh, head and senior consultant of respiratory medicine at KK Women's and Children's Hospital.

Seek medical help if your child experiences any of the following after eating: abdominal pain or bloating, chronic coughing, shortness of breath, swelling of the lips, mouth, tongue, face or throat, vomiting, nausea, itching or tightness in the throat.

If the allergic reaction is so severe that it is life-threatening, the child, parent or caregiver has to learn to immediately administer adrenaline injections, said Dr Goh.

The 'standard' allergy management methods are avoidance, medication and, occasionally, immunotherapy, said Dr Lee.

Avoidance depends on first knowing what to avoid. This is based on observation and confirmed by an allergy test such as a skin prick test or a blood test, said Dr Lin.

Medication includes oral antihistamines, oral decongestants, antihistamine eye drops and nasal sprays.

As for immunotherapy (desensitisation),

Dr Lee said, 'it has been available for decades in the form of daily injections. Now, it can be done via liquids placed under the tongue'. Its aim is to reduce the body's antibody response to the various allergens.

'Immunotherapy is the closest thing to a 'cure' for allergies. But only certain allergies (for example, dust mites, pollen and insect stings) can be treated using this method,' said Dr Lin.

It is also not a quick fix. It takes as long as three to five years for the body to be desensitised to the allergens, he said.

This article was first published in Mind Your Body, The Straits Times on Jun 11, 2008.