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A food allergy will usually cause some sort of reaction every time the offending food is eaten. Symptoms can vary from person to person, and you may not always experience the same symptoms during every reaction.

This was shared by the Nutrition and Dietetics Department, and the Allergy Service, both departments from KK Women’s and Children’s Hospital (KKH), a member of the SingHealth group. 

Symptoms of an allergic reaction may involve the patient’s skin, gut, airway, breathing and circulation. They can present in one or more of the following ways:

  • Skin: Hives, rashes, swelling of the eyes, face and/or mouth (Angioedema)

  • Gut: Vomiting, diarrhoea, reflux, trouble swallowing

  • Airway and Breathing: Repetitive cough, wheezing, shortness of breath, breathing difficulty, tight and/or hoarse throat

  • Cardiovascular/Circulation: Sudden drop in blood pressure, dizziness or feeling faint

  • Anaphylaxis: a potentially life-threatening reaction that can affect the patient’s airway, breathing and circulation (A, B, C)

The severity of symptoms varies from mild to severe. Mild to moderate symptoms can be treated by antihistamines. However, in the event of severe anaphylaxis, the first line treatment is an injection of adrenaline. Some patients may hold a personal adrenaline auto-injector such as an Epipen.

How are food allergies diagnosed

To make a diagnosis, your doctor will take a detailed allergy-focused history which includes questions such as: ask detailed questions about your medical history and your symptoms. Be prepared to answer questions about:

  • Medical and family history
  • Type and amount of food consumed
  • Time to onset of symptoms
  • Type of symptoms

After taking your history, your doctor may ask you to see an allergy doctor (allergist). Your allergist may conduct tests to help in the diagnosis of the food allergy.

Examples of allergy tests are:

  • Skin prick tests: A small amount of liquid containing the food allergen is placed on the skin of the arm or back, and then pricked
  • Specific IgE levels: Measures the amount of IgE antibody to the specific food(s) being test

In some cases, an allergist may wish to conduct an oral food challenge, which is considered the most accurate way to make a food allergy diagnosis. During an oral food challenge, the patient is fed the suspected offending food in increasing doses over a period of time while under constant monitoring.

This is followed by a few hours of observation to monitor for possible reactions. This test is helpful when the patient history is unclear or if the skin or blood tests are inconclusive. It also can be used to determine if a food allergy has been outgrown. Due to the possibility of a severe reaction, an oral food challenge should be conducted only by experienced allergists in a clinic or hospital setting, with emergency medication and equipment on hand.

In recent years there has been an increase in alternative food allergy tests, such as the IgG antibody blood testing. There is no scientific evidence to support to use of such tests in the diagnosis of food allergy.

How to manage food allergies

For most people with food allergies, identifying and avoiding the offending food is the key to avoiding a food allergic reaction. This involves reading food labels to check if the product contains the food allergen(s), and preventing cross-contamination during food preparation. 

  • Reading food labels
    Always check the information on the food item itself as recipes for food products may change from time to time. If you have questions or unsure about the safety of the food, call the manufacturer or avoid eating it

  • Preventing cross-contamination
    Cross-contamination happens when the offending food allergen comes into contact accidentally with another allergen-free food during food preparation. Even a tiny amount of food can result in an allergic reaction. Some measures to prevent cross-contamination includes washing hands before and during food preparation, washing utensils, cutting boards and crockeries thoroughly with soap and water

Outgrowing food allergies

Children generally, but not always, outgrow allergies to milk, egg, soy and wheat. New research indicates that up to 20 percent of children may outgrow their peanut allergy, with slightly fewer expected to outgrow a tree nut allergy. If a food allergy develops as an adult, the chances of outgrowing the allergy are much lower. Food allergies in adults tend to be lifelong.

Although most food allergies develop when you are a child, they can, rarely, develop as an adult. The most common food allergies for adults are shellfish – both crustaceans and mollusks – as well as tree nuts, peanuts and fish. Most adults with food allergies have had their allergy since they were children.

It is essential for children with food allergies to be regularly monitored by an allergist to determine if they have outgrown their food allergy.

Food allergies and growth

Children with food allergies are potentially at risk of poor growth, especially those with cow’s milk protein allergy, multiple food allergies or moderate-severe eczema. This is due to elimination of multiple foods from the diet which restricts dietary variety and nutrient intake.

How an allergy dietitian can help

An allergy dietitian will assess your child’s growth and nutritional intake, comparing it to his/her needs. Apart from being equipped with knowledge regarding the types of allergen-containing foods to avoid, an allergy dietitian is also able to suggest appropriate and safe substitutes to ensure your child maintains a well-balanced and nutritious diet to support his/her growth and development.

They can help to ensure that parents can be equipped with adequate self-management skills such as label reading and practical strategies to prevent cross-contamination.

What to do if you're unsure if it’s a food intolerance or food allergy?

It is important to consult your doctor to accurately diagnose food allergies and avoid unnecessary food restrictions, which can result in poor nutrition for your child. Regular follow-ups with the allergist are also essential so that your child and his/her food allergy can be monitored closely.

Read on for information on lactose intolerance on the next page.

Ref: M19