Food Allergy

Food allergy is an abnormal response to a food triggered by our body's immune system. It affects children and adults.

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Causes of Food A​​llergies

It is caused by food allergens, which are food proteins that cause allergic reactions. Immunoglobulin E (IgE) is a type of protein in our immune system that works against a specific type of food. Allergic reactions to food can be classified as IgE-mediated or non-IgE mediated.

IgE-mediated

  • Can be sudden, unexpected and life-threatening

  • A tiny amount of allergen can trigger a reaction

  • Continues to occur with re-exposure to the particular food

Non-IgE mediated

  • Exact mechanism not well understood

  • Generally uncommon

  • May have a delayed onset (several hours to days) after exposure to a particular food

Symptoms

IgE-mediated
Common symptoms include:

  • Itching in the mouth

  • Swelling of the lips, face, tongue, throat or other parts of the body

  • Flushing, itching of the eyes, hives or eczema

  • Abdominal cramps, diarrhoea, nausea or vomiting

  • Throat tightness

  • Breathing difficulties

  • Giddiness, faintness or loss of consciousness

Anaphylaxis

  • Severe allergic reaction that can be fatal if left untreated

  • Diagnosed when there is difficulty in breathing and severe drop in blood pressure, resulting in giddiness and / or loss of consciousness

  • May occur without usual symptoms of itchy rashes and swelling of eyes and lips

  • Life-threatening and requires immediate medical attention. Call 995 for an ambulance.

Oral allergy syndrome

  • For those with pollen allergies

  • Raw food and vegetables trigger allergic reaction that causes itching in the mouth

  • May cause swelling of the throat and even anaphylaxis

  • Cooking the food and vegetables may help avoid this reaction


Exercise-induced food allergy

  • Allergic reaction triggered by exercise after eating foods such as wheat or shellfish

  • Staying away from certain foods and not eating a few hours before exercise may help avoid this reaction

Non-IgE mediated
Common symptoms include:

  • Vomiting

  • Abdominal pain

  • Mucus and blood-stained diarrhoea

  • Iron deficiency anaemia

  • Eosinophillic Oesophagitis

  • Causes inflammation of the food pipe

  • Causes swallowing difficulties, reflux symptoms, abdominal cramps and vomiting in young children

  • They may also have associated allergic dermatitis, allergic rhinitis and asthma

  • Elimination diets and fully pre-digested (elemental) formula may help in some cases

Common Allergenic Foods


  • Eggs

  • Soybeans

  • Peanuts

  • Cow's milk

  • Tree nuts

  • Fish

  • Unique food allergens 

    • Edible bird's nest from swiftlets

    • Royal jelly

    • ​Buckwheat

Related: ​Eating Wrong Food Can Create Problems

Food intolerance

Food intolerance does not involve the immune system and are usually not life threatening. Some of these reactions are caused by an inability to digest a particular food. Common food intolerance are for lactose and gluten. Some sensitive individuals also react to food additives and components.

If you have a food allergy, you will suffer a reaction even if you consume a small portion of the food you are allergic to. If your reaction is more of intolerance, you may be able to tolerate small amounts of the offending food without a reaction.

Coping with food sensitivities

If you or a close family member suffers from a food reaction, you will know how distressing it can be especially when the trigger is not identified. An accurate diagnosis is very helpful in avoiding the discomfort and risks. It will also help the sufferer to eat a more balanced diet and enjoy a variety of other food without fear.

For a proper diagnosis of your food reaction, you must see a qualified medical doctor as it requires skill to pinpoint the cause of a food reaction and make a clear distinction between food allergy and food intolerance.

The specialist will conduct a comprehensive history (including the review of a detailed food diary), physical examination, and order several tests such as skin tests, blood tests such as the measurement of blood counts and total IgE, pulmonary function tests and others, as needed. After the tests, the specialist will offer the diagnosis and treatment plan, answer any questions and arrange follow-up sessions.

Some of the simple but effective strategies to cope with food reactions are as follows:

  1. Avoid allergens

    Since true allergies involve the immune system and can trigger severe reactions, it is best to avoid any food or ingredient that causes allergy. With accurate diagnosis and a strict exclusion diet, individuals with food allergies can cope pretty well with life. To prevent unnecessary food exclusion, careful food challenges can be conducted under the supervision of a qualified medical practitioner, to confirm food allergies.

    As food allergies last a lifetime, it is important to replace the potential food allergen with a nutritionally equivalent substitute. This is particularly important in the diet of individuals who are allergic to many food.

  2. Lactose intolerance

     

    Lactose is a sugar found in milk, and all healthy babies produce an enzyme known as lactase to help digest lactose. For the majority of Asians, our bodies naturally stop producing lactase as we grow up, a condition known as lactase non-persistence. People with lactase non-persistence can still drink milk without suffering symptoms of intolerance.

    Individuals with lactose intolerance will suffer from flatulence, stomach cramps, bloating, discomfort and diarrhoea.

    Here are some simple ways to help those who want to drink milk:

    • Continue to consume milk and dairy products beyond the age of 2 years. This will help the friendly bacteria in the large intestine to adapt and break down milk sugars, relieving you of stomach pain and diarrhoea when you consume a small amount of lactose.
    • Have milk and other dairy products with other food (e.g. milk with cereal).
    • Select fermented dairy products (e.g. yoghurt or cheese) as the lactose content of these products is lower than that in milk.
    • Have milk in small quantities. Drinking half a cup (125 ml) or less at a time will help to reduce symptoms of lactose intolerance as you may have enough of the enzyme in your gut to help you break down the milk sugar in this small portion.

    If you do avoid milk and milk products, then be careful to include other calcium-rich food such as fish with edible bones, soybean curd, green leafy vegetables and other calcium-fortified food.

  3. Wheat intolerance

    Some people react to wheat or to just the protein in wheat called gluten. If you are sensitive to or intolerant of wheat, then avoid the grain. But this is easier said than done as wheat is incorporated into a variety of everyday food such as bread, biscuits, cakes, pastries and a variety of noodles including, yellow noodle. To prevent a reaction, try to identify which of the food that you eat regularly contain wheat and avoid these.

    Gluten intolerance is even more difficult to manage as gluten is found in a variety of grains such as wheat, oats, rye and barley. Eliminating all these food may make meal planning difficult. Switching to rice-based products is helpful. Some supermarkets in Singapore do carry a range of gluten-free products that may make the diet less monotonous.

  4. Other food insensitivities

    Every individual is different. Some react to food additives and others to natural components in food such as caffeine. The best way to track the offending food down is to keep a detailed food and symptom diary. Careful observation can provide some clues. Try an elimination diet to check for symptom relief. Confirm the suspicion by challenging yourself with a standard portion. Resurgence of the symptoms will help you confirm the food you cannot tolerate.


Diagnosis

Detailed history of patient's symptoms, suspected food allergens and a family history of food or other allergies are very important in the diagnosis.

Investigations for confirming responsible suspected foods include:

  • Skin prick test

  • ​Blood test

Further confirmation done through:

  • Elimination diet (suspected foods eliminated for a week or two then added back into diet one at a time)

  • ​​Food challenge test (helps confirm or rule out allergies when diagnosis is doubtful)


Treatment

  • Avoid foods that cause signs and symptoms

  • Elimination of suspected foods (after a confirmed skin prick test or blood test)

  • Working with a doctor for a written action plan that describes:
    • ​How to avoid potential trigger substances

    • How to recognize and manage early stages of a reaction

    • When to alert key people around

    • When to have a long-term follow-up


For severe reactions such as anaphylaxis:


  • Self-injectable epinephrine every 5-15 minutes as needed

  • Person must be immediately transferred to seek emergency care

  • May need to be observed for up to eight hours after first episode due to risk of second reaction

Related: Antihistamines

​Prevention

The best way is to know and avoid foods that cause signs and symptoms.

If you know you have a food allergy:

  • Read food labels for ingredients

  • Wear a medical bracelet or pendant

  • Carry your emergency epinephrine

  • Ask what the ingredients are when dining out

If you have a family history of food allergy, your child will have a greater chance of being allergic. Some ways to reduce the risk in them include:

  • Breastfeed the baby for the first four months

  • Use a hydrolysed formula if baby is unable to be completely breastfed (not recommended in place of exclusive breastfeeding)

  • Introduce solids to the baby after four months of age

  • Avoid dietary restriction during pregnancy or lactation if you have a family history of food allergies

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