Food Allergy

There are two main groups of food allergy

1. Immediate-type (IgE-mediated) food allergies which are more common
2. Delayed type (non-IgE-mediated) food allergies which are less common

These types of allergies present quite differently as they have very different underlying mechanisms (See what is an allergy).

Immediate type (IgE-mediated) food allergy

This is the most common type of food allergy. Reactions occur from minutes up to 2 hours after eating the food. Some people react to tiny amounts where others react to larger amounts. The amount varies between people but also may vary within the same person on different occasions. People with very severe allergy may react with tiny doses that contaminate another food, or that they come into contact with by being kissed by someone who has just eaten the food or by food particles in the air when someone is cooking that food! Itchy skin, a red rash, flushing and swelling of the skin around the eyes or other parts of the body. Swollen, watering or itchy eyes. Swelling of the lips or tongue, vomiting, diarrhoea or abdominal cramps. Sniffing and sneezing, wheezing or asthma attacks, noisy or difficult breathing. Anxiety, children being withdraw and a “feeling of doom”. Fast heartbeat, low blood pressure, fainting or collapse.

Immediate type (IgE-mediated) may cause:

When the circulation or the airway is involved, the allergic reaction is severe, known as anaphylaxis (pronounced an-a-fi-LAK-sis). This can occur very quickly and is a medical emergency.

Immediate allergies occur most commonly to:

• Milk
• Hen’s egg
• Peanuts and other nuts
• Fish
• Shellfish
• Soya
• Wheat

Immediate-type (IgE-mediated) food allergy

This is the most common type of food allergy. Reactions occur from minutes up to 2 hours after eating the food.

Some people react to tiny amounts whereas others react to larger amounts. The amount varies between people but also may vary within the same person on different occasions.

People with very severe allergies may react with tiny doses that contaminate another food, or that they come into contact with by being kissed by someone who has just eaten the food or by food particles in the air when someone is cooking that food!

Immediate (IgE mediated) allergy may cause:

Itchy skin, a red rash, flushing and swelling of the skin around the eyes or other parts of the body.

• Swollen, watering or itchy eyes
• Swelling of the lips or tongue, vomiting, diarrhoea or abdominal cramps
• Sniffing and sneezing, wheezing or asthma attacks, noisy or difficult breathing
• Anxiety, children being withdrawn and a “feeling of doom”
• Fast heartbeat, low blood pressure, fainting or collapse

When the circulation or the airway is involved, the allergic reaction is severe, known as anaphylaxis (pronounced an-a-fi-LAK-sis). This can occur very quickly and is a medical emergency.

Delayed type (Non IgE mediated) food allergy

This type of allergy is less common than immediate type food allergy. It occurs hours to days after eating the offending food and is often more difficult to recognize. (See delayed food allergy).

CROSS REACTIONS

People who are allergic to one food may react to a similar protein found in something else. For example, peoplewho are allergicto peanuts are often allergicto tree nuts or sesame.Some people with hayfever from tree, grass or weed pollens may develop reactions to certain fruits or nuts (see oral allergy syndrome pamphlet). This is known as cross-reactivity. Cross-reactivity happens when the immune system thinks one protein is closely related to another.

People who are allergic to one food may react to a similar protein found in something else. For example, people who are allergic to peanuts are often allergic to tree nuts or sesame. Some people with hayfever from tree, grass or weed pollens may develop reactions to certain fruits or nuts.

This is known as cross-reactivity. Cross-reactivity happens when the immune system thinks one protein is closely related to another.

If a reaction occurs every time a food is eaten it is more likely to be a true immediate type food allergy. Diagnosing food allergy rests on careful evaluation of the patient together with test results.

In immediate type allergies, skin prick tests or blood tests (which detect IgE antibodies to various foods in the blood) may be very useful (See skin prick testing). However it is critical to remember that a “positive” skin or blood test does not necessarily mean the person is allergic … this may occur when someone is “sensitized” to the food and has some antibodies, but is able to eat the food in any case because other mechanisms in the body are making them tolerant.

If the diagnosis is uncertain an “oral food challenge” may be necessary.

In an oral food challenge, increasing amounts of the food are given under close supervision in a clinic or hospital. The person will either “fail” the challenge by having a reaction, or will “pass”
the challenge by being able to eat a full age-appropriate portion. This is sometimes to only way to check whether someone is truly allergic to a food (see oral food challenges).

In recent times, there have been a myriad of non-scientific diagnostic tools and methods that have been promoted. However, there is absolutely no evidence that ALCAT, Vega testing, pulse testing or kinesiology are of any benefit in diagnosing food allergy. People who use these tests may spend a lot of money to receive an incorrect list of foods to avoid and risk their nutrition.

There is no “cure” for food allergies. People with an allergy need to avoid that particular food (or foods). They must read all food labels carefully (see individual food allergy sheets). At the same time it is essential to provide a balanced diet with enough protein, energy, minerals and vitamins.A qualified dietician may be able to guide you on how to ensure this. Some younger children do outgrow their allergies, hence annual testing is recommended. For people with severe immediate-type reactions the patient must know how to recognize and treat an allergic reaction, in case they accidentally eat this food. To help them, AFSA has an emergency action plan that details how to recognize a reaction and how to treat it. (See anaphylaxis action plan).

Milder reactions, just an antihistamine is given. For more severe reactions, a dose of adrenaline is given by injection into a muscle. Your doctor will advise if you are at risk of severe reactions and whether you need a mediband bracelet or an adrenaline pen. Medibands are available on the AFSA website at https://www.allergyfoundation.co.za/what-we-offer/afsa-approved-products/

Patients with food allergy must see a doctor with experience in food allergies regularly. The doctor will check whether they are managing to avoid the food, whether accidental reactions are
being treated properly, whether the risk of severe reactions has changed and whether there are signs that the allergy may be outgrown. If the doctor thinks there is a chance of the allergy being outgrown s/he may repeat skin or blood tests and then do an oral food challenge test.

There are different types of non-immune reactions to food. Some people with food intolerance will tolerate small amounts of a certain food, only to become symptomatic if they have too much of it, for example wheat in people with irritable bowel syndrome. Some people may lack the enzymes to digest certain foods. The commonest example is lactose intolerance where the “lactase” enzyme used to break down milk sugar lactose is missing. This causes cramping and diarrhoea after eating dairy products. Non-allergic food intolerance may also be caused by preservatives, flavouring agents such as monosodium glutamate (MSG), colouring agents such as tartrazine and preservatives such as sulphur dioxide and benzoates. A medical specialist with a special interest and skill in allergy might be able to help. See the list of health professionals with skills in allergy on the AFSA website directory.

Please find the specific Food Allergies, and related conditions as follows:

• Alpha Gal
• Coeliac Disease
• Delayed type food allergy
• Food allergy
• FPIES
• Cows Milk allergy
• Egg allergy
• Fish & Seafood allergy
• Food additives
• Peanut allergy
• Soy allergy
• Testing for allergy
• Anaphylaxis and how to treat
• Immunotherapy
• Anaphylaxis Action plan

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