Allergy

A food allergy is an abnormal reaction of the immune system that occurs in response to otherwise harmless substances such as milk and eggs. Food allergy-related disorders can mimic allergies but do not involve the immune system.

Allergies are caused by the presence of specific IgE antibodies directed against allergens. These antibodies bind to mast cells that are present in the lining of the lung, gastrointestinal tract and skin. When the cell-bound IgE meets an allergen, the mast cell releases a series of very powerful chemicals, including but not limited to histamine. This causes allergic symptoms such as asthma, diarrhoea or eczema.

A food allergy can be diagnosed by doctors and dietitians using a skin prick test or blood test, together with a history of reaction shortly after eating a suspected food. The gold standard for diagnosis is a food challenge.

Food allergy-related disorders are usually diagnosed by doctors and dietitians when assessing a history of symptoms developed after eating – sometimes hours later. A detailed food diary can also help, followed by dietary elimination and food re-introduction with/without food challenges.

A food challenge involves giving suspect foods to patients in a carefully graded and supervised manner every 15-30 minutes until symptoms appear or a predefined dose is reached.

Anaphylaxis is a severe form of allergic reaction that results in a drop in blood pressure, asthma, throat swelling with difficulty in breathing, abdominal pains, skin rashes or collapse. It is considered to be an emergency and requires immediate administration of adrenaline. The common causes of anaphylaxis are foods and drugs.

The risk of developing allergies is greater if there is a family history of allergies. However, there is no certainty that children will inherit an allergy from their parents.

Skin prick tests are used for diagnosis of inhaled and ingested food allergies (e.g. pollen, cats, house dust mites, milk, eggs, nuts). Intradermal tests are used mainly for drug allergies (e.g. aspirin) and bee/wasp venom allergies. Patch tests are used to diagnose causes of contact dermatitis (e.g. shampoo, skin care products, etc.). Skin prick and intradermal tests generally take a few minutes to perform, while patch testing requires a few days for a full assessment.

FENO stands for Fractional Expired Nitric Oxide, and its concentration is measured in the air you exhale. The FENO test reflects the degree of eosinophilic inflammation in the airways. The higher the level, the more severe the inflammation. It is a non-specific test for conditions such as asthma. The FENO test is very sensitive to inhaled steroid therapy, so when the drug improves the degree of airways inflammation the FENO level will come down.

By monitoring your symptoms and conducting FENO and lung function tests, your doctor can effectively manage and treat your asthma.

Desensitisation is a technique that allows sufferers to be less allergic to specific substances, such as pollens, house dust mites or certain foods. There are two major approaches: by subcutaneous injection and the oral route of the allergen. The oral route involves either sublingual administration or food ingestion (if it is a food allergy). The general principle is to give an allergen slowly and regularly over several months (the induction phase) to reach a maintenance dose. The maintenance dose is then administered on a regular basis for 3 years.

Yes, it is safe. However, side effects can occur, so the treatment must be supervised by experienced specialists and conducted in an environment where any allergic problems that arise can be treated immediately.

Long-term use of steroid ointments and pills will cause side effects, but treatments usually involve not enough steroids to harm the patient. However, this often results in poor resolution of the inflammation and may mean using more steroids in the medium term than if the problem had been treated properly at the start. Your doctor will advise you on the safe and appropriate level of steroids you should be taking.