Food allergies: symptoms
A food allergy is a response by the body’s immune system to a particular food. The immune system responds to the food as if it were toxic.
Food allergies can occur immediately (immediate onset) or after some time has passed (delayed onset).
Immediate-onset food allergies
The symptoms of immediate-onset food allergies usually appear within a few minutes. But sometimes symptoms can appear up to two hours after a child has eaten the food.
Symptoms of immediate-onset food allergies include:
- skin reactions like redness, hives or eczema
- itchy mouth or eyes
- vomiting, stomach pain or diarrhoea
- nasal congestion
- swollen lips or tongue, which can make it hard to breathe
- swollen face, including swelling of eyelids and face
- anaphylaxis or anaphylactic shock.
A child with anaphylaxis might have a persistent cough, wheezing, hoarse voice, shortness of breath and difficulty swallowing. The child might even pass out.
Delayed-onset food allergies
The symptoms of delayed-onset food allergies appear more than 2-4 hours after a child comes into contact with the food and sometimes many days later.
Symptoms of delayed-onset food allergies include vomiting, diarrhoea, bloating and stomach cramps. This usually isn’t life threatening.
Anaphylaxis is a life-threatening allergic reaction and requires urgent medical attention. If your child is having an anaphylactic reaction, first lay him flat to help keep his blood pressure stable. Next use an adrenaline auto-injector like EpiPen® if one is available. Then call an ambulance – phone 000.
Food intolerance: symptoms
A food intolerance is a reaction in your body that’s caused by a substance in the food you’re eating. It isn’t caused by your immune system responding to the food. It often has a delayed onset.
Symptoms of food intolerance appear up to two days after exposure. They can include bloating, diarrhoea and stomach pain.
What to do about food allergies
There’s no cure for food allergies, but many children grow out of them. You can also take some steps to make it easier for you and your child to live with food allergies.
Avoid the food
It’s important to avoid the food. This can be challenging, particularly if eating even tiny amounts causes a reaction. Your child also needs to avoid any foods or cutlery that could have been in contact with the food she’s allergic to.
You can do two important things to help your child avoid the food:
Read labels on all foods. Be aware that some allergenic foods have different names – for example, cow’s milk protein might be called ‘whey’ or ‘casein’. But by law the 10 most common allergens need to be plainly stated on food labels – for example, cow’s milk, soy, egg, wheat, peanuts and tree nuts.
Be careful when you eat out. Ask what ingredients each dish includes, how it was prepared, whether it has touched any other foods, and whether there’s any risk of cross-contamination. Most restaurants are happy to tell you, but they might not know about the ingredients in some foods like sauces.
It’s best to avoid buffets and bain-maries (food warmers) because there’s a good chance ingredients have been transferred from one dish to another.
Have an emergency plan
You should talk to your doctor about an emergency plan. This will help you recognise and treat symptoms if your child eats something that causes an allergic reaction.
- Your doctor might suggest your child wears a medical bracelet that explains his allergy.
- If your child’s allergy carries a risk of anaphylaxis, she might be prescribed an adrenaline auto-injector, which makes it easy to self-inject adrenaline. Your doctor will teach you and your child (if old enough) how to use the adrenaline auto-injector.
- It’s important that key people – like family, carers, babysitters and your child’s school – know how and when to use your child’s adrenaline auto-injector.
What to do about food intolerance
Symptoms of food intolerance are usually less severe than those of allergies, and these symptoms don’t cause anaphylaxis.
If a doctor has diagnosed food intolerance in your child and your child eats something you know he’s intolerant of, he shouldn’t need urgent medical attention. The symptoms will usually clear up by themselves. If your child’s symptoms include diarrhoea, you need to make sure he gets plenty of water.
If you’re not sure why your child is having a reaction, and there’s a possibility the reaction could be caused by a food allergy, it’s best to consult your doctor.
Diagnosing food allergies and food intolerance
If you think your child has a food allergy or intolerance, your GP is the best place to start. Your GP might refer you to an allergist for further checks and tests.
Immediate-onset food allergies
Tests for immediate-onset allergies include the following:
Skin-prick test (SPT): the allergist will put a small amount of the possible allergy-causing substance on your child’s skin. Then the allergist will prick your child’s skin with a small toothpick-like device. A red lump might come up where the skin has been pricked.
Blood tests: the serum specific IgE antibody test uses your child’s blood to see whether she’s sensitive to specific allergens. Your child might have this test if she can’t have skin-prick testing because she has severe eczema or has taken an antihistamine.
Oral food challenge: your child will be given the possible allergy-causing food to eat in a safe, supervised setting. Medical and nursing staff will watch to see whether an allergic reaction occurs. This test carries a risk of causing a severe allergic reaction and should be conducted only by a specialist in a supervised setting.
Delayed-onset food allergies
If your child has a delayed-onset food allergy, testing is more difficult.
The most common test is the ‘elimination and rechallenge’ test. This involves removing possible allergy-causing foods from your child’s diet, then reintroducing them if the allergist thinks it’s safe to do so. You reintroduce only one food at a time so it’s easier to identify the food that’s causing the allergy.
Once you know which food is causing the allergy, your child can avoid that food.
Elimination diets are also the most common test for food intolerance.
For suspected fructose or lactose intolerance, doctors might also use a breath test. This tests the amount of hydrogen gas in the child’s breath. Lactose-intolerant children will have higher levels of hydrogen in their breath.