A food allergic reactions is when the body’s immune system reacts unusually to specific foods. Although allergic reactions are often mild, they can be very serious.
Symptoms of a food allergy can affect different areas of the body at the same time. Some common symptoms include:
- an itchy sensation inside the mouth, throat or ears
- a raised itchy red rash (urticaria, or “hives”)
- swelling of the face, around the eyes, lips, tongue and roof of the mouth (angioedema)
In the most serious cases, a person has a severe allergic reaction (anaphylaxis), which can be life threatening.
If you think someone has the symptoms of anaphylaxis – such as breathing difficulties, lightheadedness, and feeling like they’re going to faint or lose consciousness – call 999.
Ask for an ambulance and tell the operator you think the person has anaphylaxis or “anaphylactic shock”.
What causes food allergic reactions?
Food allergic reactions happen when the immune system – the body’s defence against infection – mistakenly treats proteins found in food as a threat.
As a result, a number of chemicals are released. It’s these chemicals that cause the symptoms of an allergic reaction.
Almost any food can cause an allergic reaction, but there are certain foods that are responsible for most food allergies.
In children, the foods that most commonly cause an allergic reaction are:
Most children that have a food allergy will have experienced eczema during infancy. The worse the child’s eczema and the earlier it started, the more likely they are to have a food allergy.
In adults, the foods that most commonly cause an allergic reaction are:
- tree nuts – such as walnuts, brazil nuts, almonds and hazelnuts
- fruits – such as apples and peaches
- shellfish – such as crab, lobster and prawns
Read more information about the causes and risk factors for food allergies
Types of food allergies
food allergic reactions are divided into three types, depending on symptoms and when they occur.
- IgE-mediated food allergy – the most common type, triggered by the immune system producing an antibody called immunoglobulin E (IgE). Symptoms occur a few seconds or minutes after eating. There’s a greater risk of anaphylaxis with this type of allergy.
- non-IgE-mediated food allergy – these allergic reactions aren’t caused by immunoglobulin E, but by other cells in the immune system. This type of allergy is often difficult to diagnose as symptoms take much longer to develop (up to several hours).
- mixed IgE and non-IgE-mediated food allergies – some people may experience symptoms from both types.
Oral allergy syndrome (pollen-food syndrome)
Some people experience itchiness in their mouth and throat, sometimes with mild swelling, immediately after eating fresh fruit or vegetables. This is known as oral allergy syndrome.
Oral allergy syndrome is caused by allergy antibodies mistaking certain proteins in fresh fruits, nuts or vegetables for pollen.
Oral allergy syndrome generally doesn’t cause severe symptoms, and it’s possible to deactivate the allergens by thoroughly cooking any fruit and vegetables.
Some people with pollen-food syndrome may have more severe symptoms.
The Allergy UK website has more information on oral allergy syndrome.
The best way of preventing an allergic reaction is to identify the food that causes the allergy and avoid it.
Research is currently looking at ways to desensitise some food allergens, such as peanuts and milk, but this is not an established treatment.
Read more about identifying foods that cause allergies (allergens)
Avoid making any radical changes, such as cutting out dairy products, to your or your child’s diet without first talking to your GP. For some foods, such as milk, you may need to speak to a dietitian before making any changes.
A type of medication called an antihistamine can help relieve the symptoms of a mild or moderate allergic reaction. A higher dose of antihistamine is often needed to control acute allergic symptoms.
Adrenaline is an effective treatment for more severe allergic symptoms, such as anaphylaxis.
People with a food allergy are often given a device known as an auto-injector pen, which contains doses of adrenaline that can be used in emergencies.
When to seek medical advice
If you think you or your child may have a food allergy, it’s very important to ask for a professional diagnosis from your GP. They can then refer you to an allergy clinic if appropriate.
Many parents mistakenly assume their child has a food allergy when their symptoms are actually caused by a completely different condition.
Commercial allergy testing kits are available, but using them isn’t recommended. Many kits are based on unsound scientific principles. Even if they’re reliable, you should have the results looked at by a health professional.
Most food allergic reactions affect younger children under the age of three. It’s estimated around 1 in every 14 children of this age has at least one food allergy. Most children who have food allergies to milk, eggs, soya and wheat in early life will grow out of it by the time they start school. Peanut and tree nut allergies are usually more persistent. An estimated four out of five children with peanut allergies remain allergic to peanuts for the rest of their lives. Food allergies that develop during adulthood, or persist into adulthood, are likely to be lifelong allergies. For reasons that are unclear, rates of food allergies have risen sharply in the last 20 years. However, deaths from anaphylaxis-related food reactions are now rare.
- A food allergic reactions occurs when the body mounts a predictable immune response to a food. Peanuts, milk, tree nuts, eggs, wheat, soy, sesame, fish and shellfish are the most common.
- Babies are considered high-risk for developing peanut allergies, and likely others, if they have certain risk factors, such as severe eczema or another food allergy.
- If your child is high-risk, a pediatrician or allergist might recommend a blood or skin test before introducing peanuts.
- Be aware that false positives are exceedingly common on blood and skin allergy tests. A positive test requires follow-up with an allergist, who ideally will do an in-office food challenge to see if your baby is truly allergic.
- Introducing peanut products early can help prevent peanut allergy in high-risk babies. The goal for any baby is a diverse diet, including major allergens within the first year of life.
- Kids can outgrow some food allergies, and new treatments are being developed that offer hope of improving the lives of kids with persistent food allergies.
- In babies, hives and vomiting are the most common food allergy symptoms. Mild rashes or skin irritation are common and might not mean that your child is allergic to the food.