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Around 8% of children in the UK have food allergies and it’s important for a parent to be able to spot the signs early. With the help of food allergy testing and diagnosis, you will find it much easier to avoid any triggers and prevent future reactions.
Food allergy symptoms
Food allergies occur when the immune system reacts abnormally to specific proteins in foods. Reactions to a food allergen can occur immediately after your child’s exposure, or a delay can mean they do not appear for several hours. The timing can depend on how sensitive your child is to the allergen.
The signs and symptoms of food allergies in children can vary in severity and may include the following:
- drop in blood pressure, dizziness, and fainting
- nausea, vomiting, abdominal pain, diarrhoea, and bloating
- oral symptoms like tingling or itching in the mouth, tongue, or lips
- respiratory symptoms, including coughing, sneezing, runny or stuffy nose, shortness of breath, and wheezing
- skin symptoms such as hives, eczema, itching, and swelling
Children cannot always explain how they feel, so keep a close eye on their behaviour for any changes. Behavioural changes can include irritability, restlessness or general changes in mood.
Anaphylaxis
Anaphylaxis is a severe and potentially life-threatening allergic reaction that requires immediate medical attention. Symptoms of anaphylaxis include:
- chest pain
- confusion
- difficulty breathing and wheezing
- loss of consciousness
- swelling of the face, lips, tongue, or throat
- weak or rapid pulse
Anaphylaxis is a medical emergency. If you think your child is experiencing anaphylaxis, call 999 immediately.
Food allergy types
There are two types of food allergy that your child can experience: IgE-mediated (immunoglobulin E) food allergy and non-lgE-mediated food allergy.
These types of allergies differ in how they cause the immune system to react, producing different symptoms.
IgE-mediated food allergy
An IgE-mediated food allergy is the most common type of food allergy. When your child is exposed to the allergen, the IgE antibodies trigger a reaction in the immune system.
The symptoms of IgE-mediated food allergies occur very quickly and can include:
- anaphylaxis
- coughing
- hives
- itching
- sneezing
- swelling
Non-IgE-mediated food allergy
This type of food allergy does not involve the production of IgE antibodies. Instead, a delayed immune response typically occurs more than 2 hours – and sometimes, up to 72 hours – after consuming the triggering food.
Non-IgE-mediated food allergies usually have symptoms such as:
- abdominal pain
- diarrhoea
- nausea
- vomiting
Respiratory symptoms and skin problems are much less prevalent with these food allergies.
Children with food allergies can experience symptoms of both allergies, and their severity can vary.
For example, your child could have a peanut allergy and experience IgE-mediated symptoms, such as hives, immediately after exposure and then have non-IgE-mediated symptoms, such as abdominal pain, later on.
Discover our children’s allergy specialists
At Guy’s and St Thomas’ Specialist Care, we offer a range of food allergy services, including oral food challenges to help diagnose the symptoms your child has been experiencing. We also provide nutritional assessments so you can manage their condition effectively.
We are one of the largest training centres for paediatric allergy specialists in the UK, and our dedicated team will support you and your child on their food allergy diagnosis.
Food allergy tests
Several types of food allergy tests can help to diagnose your child’s allergy. The kind of food allergy test will depend on the specific food allergy they potentially have.
There are no clinical tests for diagnosing non-IgE-mediated allergies – these can only be diagnosed through a trial of elimination and reintroduction into the diet, and by monitoring symptoms. This diagnosis is typically carried out at home with a paediatric allergy specialist’s support and guidance.
Skin prick test
A skin prick test is a standard diagnostic test used to determine if your child has IgE-mediated food allergies.
How a skin prick test works
The allergy specialist places a small amount of the suspected food allergen on your child’s skin, usually on the forearm or back. They then prick the skin with a needle so the allergen can penetrate. Any symptoms are monitored to discover if your child is allergic to the food.
Allergy specialists use skin prick tests to identify potential allergens that may be causing your child’s symptoms. It is a quick and relatively simple test, so your child should not find the experience frightening. It may help if you can explain it to them beforehand so that they are relaxed and informed about what will happen.
Benefits of a skin prick test
There are several benefits to a skin prick test. For example, they are non-invasive and provide results within 20 minutes. As the allergist can deliver the test and results quickly, it works well for children nervous about going to the doctor.
Skin prick tests can also help identify food allergens easily, so you can cut them out of your child’s diet in future.
Skin prick test risks
Skin prick tests are generally safe, but there is a small risk of an allergic response occurring during them. However, doctors and allergy specialists are trained to manage potential reactions and have emergency medications available.
There may be discomfort or pain associated with the skin pricking, but it is usually minimal and temporary. Be sure to provide reassurance and distractions for your child if they are worried about it hurting.
Skin prick test results
A positive skin prick test result indicates that your child may have an IgE-mediated allergic reaction to the food allergen. However, a positive skin prick test alone does not confirm a food allergy. Previous medical history and other diagnostic tests, such as a blood test, may be needed.
Negative results do not entirely rule out a food allergy; it is possible for false negatives to occur. Your child may need further testing or an oral food challenge for a definitive diagnosis.
Food allergy blood test
Allergy specialists use a food allergy blood test to determine if your child has IgE-mediated food allergies.
How a food allergy blood test works
A blood sample will be taken from your child using a needle inserted into a vein in their arm. The blood sample is then sent to a laboratory for testing and checked for IgE antibodies to confirm the allergy.
Benefits of a food allergy blood test
A food allergy blood test has many benefits, including a quick and easy process. The procedure is relatively painless and the specialist can use numbing creams.
Food allergy blood tests can accurately diagnose a food allergy so you can remove allergens from your child’s diet.
Potential risks of a food allergy blood test
Food allergy blood tests are generally safe, but there is a small risk of complications associated with blood collection, such as bleeding, infection or bruising at the site. However, these risks are rare and usually minimal.
Food allergy blood test results
The food allergy blood test results will show any detected IgE antibodies in your child’s body released in response to an allergic reaction. Higher levels of IgE typically indicate that your child has an allergy, but it doesn’t confirm it entirely.
Other factors, like their medical history, will also be examined to ensure the results are relevant to the allergy.
Oral food challenge
An oral food challenge is a diagnostic test to confirm or rule out a suspected food allergy in children.
How an oral food challenge works
An oral food challenge is where the doctor or allergy specialist will feed your child their suspected allergenic food in a controlled, monitored environment to see the allergy symptoms first-hand.
They will usually give the food in increasing amounts with regular monitoring of your child’s symptoms. However, if a reaction occurs, then the doctor or expert will always give the correct medical care to keep your child safe.
Oral food challenges are considered the gold standard for diagnosing food allergies, as the results are rarely conflicting or inconclusive.
Benefits of an oral food challenge
There are many benefits of oral food challenges. For example, allergy experts perform them in a safe, controlled environment – so you know your child is being cared for in what could be a potentially scary situation for them. It also minimises the risk of a severe allergic reaction, as the allergen slowly increases in quantity.
They also provide a definitive diagnosis, which can be helpful when creating a treatment and management plan.
Potential risks of an oral food challenge
Oral food challenges risk triggering an adverse reaction, including severe allergic reactions like anaphylaxis. However, the specialist will be able to provide appropriate medical care to counteract a severe reaction if necessary.
Oral food challenge results
The results of an oral food challenge are based on the presence or absence of symptoms and adverse reactions during and after the challenge. If your child doesn’t experience any symptoms, it can indicate that they are not allergic to that food.
If they do experience symptoms, it can confirm the presence of a food allergy.
Locations
Our children's allergy service is located at:
Discover our children's allergy experts
From comprehensive allergy assessments to specialised interventions, our paediatric allergy experts are dedicated to providing personalised care for your child.