Food allergy

Food allergies are some of the most common allergies in the UK. It’s estimated that around two million people in the UK are currently living with a diagnosed food allergy, with countless others who have suspected but undiagnosed hypersensitivities to certain food items.  

Allergies are particularly common in babies and children, but adults can get them too. Knowing how to spot a food allergy and understanding treatment is important, especially for parents of babies or children with food hypersensitivity. 

Our adult allergy and children’s allergy services are some of the largest in the UK. We offer food allergy testing for children, including peanut allergy testing, as well as nutritional assessments, food and drug allergy treatment for both adults and children.

Our dedicated team will use their extensive experience to determine which foods you can’t tolerate and what can be done to help. 

What is a food allergy? 

An allergy is when your body reacts to a usually harmless substance. People can be allergic to many different things, including food. This can be a food that is eaten whole, or which is an ingredient present in a dish. 

When the body has an allergic reaction, the immune system triggers the release of a chemical called histamines. Histamines are what cause allergy symptoms.  

Common food allergies  

It’s possible to be allergic to any food item. However, there are some food allergies that are much more common than others. The vast majority of food allergies are triggered by certain proteins in foods including: 

• shellfish, such as prawns, lobster and crab 
• peanuts 
• tree nuts, such as walnuts, almonds and pecans 
• fish 
• eggs 
• cow’s milk 
• wheat 
• soy 

Unlike food intolerance, in a true food allergy, exposure to even a tiny amount of food  could cause you to have an allergic reaction. 

What causes food allergies? 

There are several risk factors which could increase your risk of  developing a food allergy. These include: 

Family history  

If someone in your family has been diagnosed with a food allergy or another allergic condition like eczema or hayfever, you could have a higher risk of developing a food allergy too. 

Existing allergies 

People with food allergies are two to four times as likely to have other allergic conditions such as asthma. Research suggests that eczema and food allergies are linked; eczema leads to a higher risk of developing a food allergy.  

Delayed introduction to foods 

Some people think that delaying the introduction of certain foods could reduce the risk of allergies developing, but there is no scientific evidence to support this. 

In fact, many guidelines recommend introducing common allergens regularly from as young as four to six months of age. Evidence has shown that delaying the introduction of allergens such as peanuts past six to 12 months may increase the risk of developing an allergy. 

Food allergy symptoms 

Symptoms of a food allergy can affect any part of the body or different parts of the body at the same time. Common symptoms associated with a food allergy include: 

• itchy skin or a raised skin rash (hives) 
• swelling of the eyes, lips and face 
• coughing, wheezing, breathlessness, noisy breathing, hoarse voice 
• sneezing 
• an itchy, runny or blocked nose 
• feeling dizzy or lightheaded 
• feeling sick or vomiting 
• stomach pain 
• diarrhoea 

If your symptoms are severe and include wheezing, feeling like your chest is tight, having problems breathing or your face, lips, mouth or tongue start to swell, call 999 immediately. You could be having a serious allergic reaction (known as anaphylaxis) and need immediate medical treatment. 

IgE vs Non-IgE allergies 

Food allergies can be divided into two types: IgE-mediated and non-IgE mediated.

IgE stands for immunoglobulin E — a specific type of antibody found in the human immune system. IgE allergies are a type of allergy where symptoms develop very quickly after coming into contact with the food that they are allergic to — typically less than two hours.  

Meanwhile, non-IgE allergies typically start to occur more than two hours and up to 72 hours after coming into contact with the allergen food.  

The good news is that food allergy testing including skin prick tests and specific blood tests can be used to diagnose IgE allergies. Unfortunately, this isn’t the case for non-IgE allergies, which can only be identified through a process of elimination and reintroduction.  

What’s the difference between a food allergy and food intolerance? 

Food allergies and food intolerances are often confused. However, they aren’t the same thing.  

A food allergy is where coming into contact with an allergen food causes your child’s immune system to have a reaction that includes some of the symptoms listed above.  

Food intolerance can also cause some of the same symptoms, but the reaction isn’t caused by the immune system. For example, it’s possible for a food to give you an upset stomach, but this  isn’t the result of your immune system perceiving the food to be harmful and going into overdrive.  

Depending on the type of food intolerance you have, you may be able to eat a small amount of the food without experiencing a problem. However, if you have a true food allergy, even the tiniest amount of food may trigger a reaction.  

How to test for food allergies 

If you suspect that you have a food allergy, you can speak with one of our allergy experts who can assess your symptoms and recommend the right test for diagnosis.  

It’s important to be aware that tests alone aren’t always enough to confirm a diagnosis, but are used along with a physical exam, your medical history and other factors to confirm if you have a food allergy.  

Some of the tests that are used to detect food allergies include: 

Skin prick testing 

Skin prick testing is the most common and preferred method of detecting true food allergies. It can be done during a regular clinic visit and results are available immediately. Skin prick tests are considered to be accurate and reliable when diagnosing IgE allergies.  

Specific IgE testing 

This is a specific blood test that measures the amount of IgE in your blood when you are exposed to a specific food protein.   

Oral food challenge 

This is a more complex test that involves eating pre-measured amounts of the suspected food allergen and being closely monitored for an allergic reaction.  

We offer private food allergy testing and challenges for children here at our hospital in London.  

What can you do to prevent an allergic reaction? 

Unsurprisingly, the best way to prevent an allergic reaction is to avoid contact with your food allergen. This means being extremely vigilant when it comes to what you or your child is eating.  

Always check the packaging of any new foods and re-check ingredient lists regularly in case manufacturers make any changes. If you are eating out at a restaurant, it’s important to let the person serving you know about any allergies in your group — most will ask you when you arrive or sit down.  

Treating a food allergic reaction 

The most obvious way to tackle any food allergy is to avoid allergen food. However, depending on what your is allergic to, this may be easier said than done.  

There are different types of medication that may be recommended to relieve the symptoms associated with a food allergic reaction.

Antihistamines 

Antihistamines are used to treat mild to moderate allergic reactions. They are medicines that work by blocking the effects of histamine when it is released by your  immune system when you come into contact with your food allergen. By preventing histamines from being released, allergy symptoms will be significantly reduced.  

Adrenaline auto-injector devices (AAIs)

Adrenaline auto-injectors, also known as adrenaline pens, such as EpiPen or Jext are used to treat severe food allergic reactions (known as anaphylaxis). Auto-injectors contain a dose of adrenaline to strengthen the heart and lungs and decrease the body’s allergic response. Auto-injectors are only available on prescription for people at risk of severe reactions.

If a person has an anaphylactic reaction they must be correctly positioned, lying down with their legs raised. If they have breathing difficulties and can’t lay they can sit down instead, but should not stand or move around.  

If you have an allergy it is advised to carry oral antihistamines and adrenaline auto-injectors (if prescribed) so they can administered immediately if needed.  

Allergen immunotherapy 

Allergen immunotherapy is a medical treatment for allergies that uses the idea that someone’s immune system can be trained to become less allergic to an allergen. While this treatment has been available for inhalant allergies like grass or tree pollen allergies for a long time, there is now good evidence that it can also be used for food allergies too.  

For this treatment the allergy sufferer would be given small doses of the food allergen to increase their threshold of reactivity. This treatment has been shown to reduce the severity of reaction on accidental exposure.  However, this treatment is not a cure for allergies as the treatment needs to be ongoing to maintain its effect. 

The downside to allergen immunotherapy is that it can cause allergic reactions, including anaphylaxis, when the dose of the food is taken. Therefore, it can only be performed under close medical supervision. In order to minimise this risk, the person undergoing treatment will have to strictly adhere to the golden rules of oral food immunotherapy, which include:

• no physical exercise an hour before and 2 hours after the dose
• skipping the dose on days when they are sick, tired or particularly stressed
• avoiding non-steroidal anti-inflammatory drugs (NSAIDs) on days of dosing

Allergen immunotherapy will involve tolerating allergy symptoms for some time while it takes place — until it becomes effective and they start to reduce.  

We offer private peanut allergen desensitisation for the treatment of peanut allergies in children. Palforzia is a peanut immunotherapy drug to help reduce the severity of children’s allergic reactions, find out more about peanut allergy treatment in children. 

Book an appointment with our allergy experts today 

Having a food allergy can be very stressful, particularly if your child has one. Fortunately, allergy awareness is greater than ever.

Our adult allergy service at Guy’s and St Thomas’ Specialist Care has been accredited at the highest level by the Global Allergy and Asthma European Network, which regulates EU asthma and allergy research quality. Find out more about our private allergy service for adults here.

Through our active research programme, we are established leaders in providing innovative paediatric allergy care and pioneering allergy treatments. If you suspect that your child has a food allergy get in touch with our friendly team today.