Updated: Dec 1, 2021
Allergies can be complicated and confusing, therefore it is important you seek the right professional help. There is a lot of mis-leading and wrong information on the internet regarding allergies, especially when it comes to testing. Below I'll look at the differences between the two main types of allergy we typically see and briefly touch on the types of testing available. More on allergy testing coming soon.
Food allergies are typically divided into 2 types; IgE-mediated and non-IgE-mediated. Both involve the immune system, but each presents in different ways. See the table below which highlights the main differences between the two;
Category of Food Allergy
Is the immune system involved?
Are IgE antibodies involved?
Common symptoms in babies
Swelling, Hives, vomiting, tingling or itching in the mouth. wheezing or shortness of breath. Very small amounts of food can trigger a reaction
GI Symptoms; diarrhoea/constipation, abdominal pain. Unsettledness, Reflux. Severity of symptoms is often related to the amount of food consumed
When do symptoms usually appear?
Almost always within 2 hours; but can occur within seconds to minutes of consuming the food
Hours to days after consuming food; can sometimes take 1-2 days
Can skin prick testing help diagnose the food allergy?
Can blood tests help diagnose the food allergy?
Can the allergy cause severe allergic reactions?
Non-IgE-mediated food allergy
In non-IgE-mediated allergies, symptoms usually appear after two hours or up to a few days after eating anything containing the specific food.
Some symptoms of non-IgE mediated allergy can be similar to those of IgE-mediated. Others may be less obvious and could be mistaken for something else. The signs of non-IgE-mediated allergy include:
The most common causative foods for non-Ig-mediated food allergies are cow's milk and soy proteins in infants and wheat in older children.
How are non-IgE-mediated food allergies diagnosed?
Unlike IgE-mediated allergies there are no blood or skin tests. Therefore a diagnosis is made based on the dietary and symptom history and may be confirmed by observing that the symptoms improve when the suspected food is removed from the diet. The process can take a number of weeks or months. This is then followed by a reintroduction to confirm any symptoms were caused by the offending food. Most dietitians will recommend the food should be removed for at least 4 weeks before challenging.
Food intolerances are different from non-IgE-mediated allergies. Your immune system is not involved in food intolerances and on the whole the symptoms usually affect your gut; feeling/being sick, diarrhoea, bloating and cramping. Allergies can often be confused for food intolerances; the most common being cow's milk protein allergy (CMPA). It is important to note that food intolerances in children and babies are extremely rare and usually only occur after infections. Taking the food out for 4 weeks and reintroducing gradually usually improves any symptoms.
Can children grow out of a non-IgE-mediated allergy?
Yes your child can! This is why we reintroduce the suspected food over a period of time. There is no set time course that your child will outgrow their allergy -however most children will grow out of non-IgE-mediated allergies by the time they start school.
IgE-mediated food allergy
In IgE-mediated allergies, symptoms usually appear within minutes or up to two hours after eating a certain food. This is because the immune system reacts to the specific allergen by producing IgE antibodies. Theses antibodies are produced by immune cells and activate the immune system to release chemicals such as histamines, which then trigger and immediate allergic reaction.
If your child has an IgE-mediated allergy, you may notice:
Skin symptoms; such as itchy rash, hives, swelling of tongue, face, lips or eyes
Abdominal pain, vomiting unusual stooling
Hay fever- like symptoms such as sneezing, itchy, blocked or runny nose
In severe cases, an IgE-mediated allergic reaction could lead to anaphylaxis.
Anaphylaxis is a potentially life threatening allergic reaction that comes on quickly, affects the whole body and requires medical attention straight away.
How are IgE-mediated food allergies diagnosed?
If a healthcare professional thinks your child has an IgE-mediated food allergy, they will offer either a blood or skin prick test. they may diagnose a food allergy based on symptoms recall when having a specific food if allergy testing is not advised i.e. if your child has severe eczema.
In a skin prick test (SPT), a small amount of liquid containing the suspected food protein is placed on the forearm, a tiny prick is made in the skin through the drop to see if a reaction occurs.
Your healthcare professional should explain these tests and discuss with you what would be the best option. You should not be advised to try an oral food challenge without seeing a specialist if your child has a suspected IgE-mediated food allergy.
As I mentioned before there are lots of complementary and alternative health practitioners on the internet offering tests for food allergies. Some examples include; hair analysis, kinesiology, serum-specific IgG antibody tests. Your healthcare professional should not offer these types of test for your child. There is no evidence that they can reliably diagnose a food allergy. If you have had your child tested using one of the above alternative health tests, please contact your Doctor or Dietitian before eliminating any foods from your child's diet.
Can children grow out of an IgE-mediated allergy?
Yes your child can! This would be closely monitored by your healthcare provider. Usually a blood or SPT result would be compared to a previous result. If the readings have reduced to a safe level an oral food challenge would be recommended.
Can my child have non-IgE-mediated and IgE-mediated food allergy together?
Yes children can have both types of food allergy. This usually occurs in children with severe eczema.
It is important to speak to a specialist paediatrician or allergy dietitian if you are worried about food allergies.