What are food allergies?
Food allergies can be scary. In some cases they cause severe reactions. And symptoms may start very young. Babies can develop an allergy to milk, eggs or peanuts as early as six months old. But it’s important not to let fear rule. Food allergies can be managed. If you can discover exactly what your trigger is and get to know your condition inside out.
Common food allergies
You can be allergic to any food but some food allergies are more common than others. Food packaging must make common allergens obvious in the list of ingredients. The same labelling laws cover restaurant menus. But it’s often impossible for food producers to rule out cross-contamination. That’s why you might see voluntary warnings on certain foods, such as “may contain traces of peanuts”.
There are 14 ingredients that commonly cause allergic reactions. Eggs, cow’s milk, fish, crustaceans, molluscs, peanuts, tree nuts, sesame seeds, cereals containing gluten, soybeans, celery and celeriac, mustard, lupin, and sulphites. Sulphites are food preservatives as well as occurring naturally in beer and wine-making. You may react to them if you already have allergic rhinitis or lower respiratory symptoms.
Gluten doesn’t generally cause a food allergy. But people with coeliac disease must avoid it completely. Eating less gluten may help if you have an intolerance to it.
Food allergies: It’s your immune system
Food allergy affects around 1-2% of UK adults. It starts when your immune system overreacts to proteins found in something you eat. The immune system’s job is to protect your body against bacteria or viruses that could make you unwell. But sometimes it gets it wrong. It mistakes a particular food for a threat and rushes to your defence. Your body wants to get rid of the allergen as fast as it can. That’s an allergic reaction.
How to read food labels
How food allergies develop
You don’t get a food allergy the first time you eat peanuts or shellfish or whatever your trigger is. Your immune system needs to build its defences first. It makes antibodies called Immunoglobulin E (IgE). Now you’re sensitised to that allergen. It doesn’t mean you’ll definitely develop a food allergy but you could.
If you do, the IgE antibodies will fight back whenever you meet the allergen. They’ll tell other cells to release chemicals like histamine. Various fluids and white blood cells also travel to the site of the supposed attack to help. Pretty quickly you’ll feel the typical symptoms of an allergic reaction.
How fast can you get food allergy symptoms?
Many people realise they’re having an allergic reaction within minutes or even seconds. And most symptoms show up within two hours.
One exception is a rare type of allergy to red meat that starts after a tick bite. The tick’s saliva can sensitise you to lamb, pork, beef and venison. Allergy symptoms tend to start four to eight hours after a meal and can be severe.
There’s another type of food allergy where the allergic reaction can start more slowly too – days later sometimes. Read more about non IgE food allergies below.
Typical food allergy symptoms
Allergic reactions to food can range from mild to severe. These are some of the symptoms to look out for:
- Tingling or itching in the mouth
- A raised, itchy red rash (hives) – sometimes the skin can turn red and itchy but not raised
- Swelling of the face, mouth, throat or other parts of the body
- Difficulty swallowing
- Wheezing or shortness of breath
- Feeling dizzy and lightheaded
- Feeling sick (nausea) or vomiting
- Abdominal pain or diarrhoea
- Hay fever-like symptoms such as sneezing or itchy eyes
The same person can react differently on different occasions. You may feel a bit unwell one time but need immediate medical treatment another. That’s why it’s important to see your GP if you suspect you may have a food allergy.
Food allergies: what is a severe allergic reaction?
Have you heard of anaphylaxis (pronounced ana-fil-ax-is)? It’s a sudden and severe and often sudden allergic reaction that can be life-threatening. Having this type of reaction once increases the chances of it happening in the future. So does a family history of severe reactions and having asthma or allergies. Call 999 if you spot the warning signs and symptoms of anaphylaxis:
- Feeling lightheaded or faint
- Difficulties with breathing, such as fast or shallow breathing
- A fast heartbeat
- Clammy skin
- Confusion and anxiety
- Collapsing or losing consciousness
Some people can get these symptoms if they play sport after eating a particular food. It’s called food dependent exercise related anaphylaxis and luckily it’s fairly rare.
Symptoms of Non IgE food allergies
This type of food allergies do not involve IgE antibodies. Protective white blood cells called T cells lead the allergic reaction. Symptoms often affect your skin and your digestion. You may get heartburn, indigestion, vomiting or diarrhoea hours or even days after eating.
Non IgE food allergy symptoms are not usually severe but they can make children reluctant to eat. And that increases the risk of developing other health issues over time. Conditions include:
- Food protein-induced allergic proctocolitis
- Food protein enteropathy
- Eosinophilic esophagitis
- Food protein-induced enterocolitis syndrome
In mixed IgE and non-IgE mediated food allergies both mechanisms play a part. You may also get both types of symptoms.
Food allergy symptoms or cross-reaction?
Certain fruit, vegetables, nuts and spices can make your lips tingle without being your main allergy trigger. The root cause is actually pollen allergy. That’s why this type of cross-reactivity is called pollen food syndrome (PFS). Another name is oral allergy syndrome (OAS). It happens because the food contains a protein very like the one in your problem pollen. Say grass pollen gives you hay fever. Well, you might get a mild local reaction in your lips, mouth, or throat when you eat tomatoes.
People might experience pollen food syndrome when eating foods such as almonds, hazelnuts, peanuts, and soybeans. But these are also major causes of food allergy. So talk to your GP straightaway if it happens.
In rare cases people with dust mite allergy can have cross-reactions when eating certain foods. It can happen with shrimp, crab and lobster, but also clams and oysters as these foods contain proteins similar to the ones in dust mites. There is also a rare type of cross-reaction between cat allergens and pork. It usually happens quickly, has the same symptoms as IgE food allergies and can be life-threatening. It’s a reaction called pork-cat syndrome.
So how do I find out if I have food allergies?
Allergy testing is often the first step. That might be a skin prick test which involves putting a drop of liquid containing the allergen onto your arm, pricking the skin underneath it gently and checking for a reaction. Or you may need an allergy blood test to look for IgE antibodies. This will show if you’re sensitised to any food allergens. The GP will ask about your symptoms and family history before making a diagnosis. It can be helpful to keep food and symptom diary.
Non-IgE food allergies are harder to diagnose. Your healthcare provider may suggest an oral food challenge. This involves giving you increasing amounts of an allergen while watching for symptoms. Or they may want to do an internal examination with a camera (endoscopy). It depends on your medical history.
Food allergies are not the same as food intolerances
Allergy testing can’t tell you if you have a food intolerance. That’s when your body struggles to digest a substance such as histamine, lactose, or gluten. It’s nothing to do with the immune system.
Food intolerance symptoms are usually mild to moderate. They also tend to start more slowly than with food allergies. You may even find you can eat a small amount of the problem food without feeling unwell. In food allergies, even a tiny trace can cause a reaction. The usual way to diagnose a food intolerance is with an elimination diet. But there are breath and blood tests to identify lactose intolerance.
How to manage food allergies
Don’t change your diet without talking to your doctor or allergist. They’ll work out a treatment plan with you. This is likely to be a mixture of avoiding your triggers and treating the symptoms when you haven’t been able to. Antihistamine blocks the effect of the histamine your body releases as part of an allergic reaction. It is a common treatment for milder allergy symptoms. Ask your pharmacist for advice about the different types available over-the-counter.
If your GP thinks you’re at risk of a severe reaction they’re likely to prescribe an auto-injecting adrenaline pen to carry with you at all times. You could also think about wearing an allergy necklace or bracelet so people know how to help you in an emergency.
Food allergies: 6 ways to avoid your triggers
We’ve talked about how to read food labels to help avoid common food allergy triggers – that is, very carefully. And the importance of teaching children to do the same. There are other good habits to get into that can help reduce the risk of having an allergic reaction both at home and on the go.
- Check non-food products: Skincare, cosmetics, petfood, vitamins, even modelling clay and finger paint can all include food allergens.
- Be allergy aware when eating out: Get in touch with the restaurant beforehand to discuss exactly what you need from them not to have an allergic reaction. Help-yourself food counters like salad bars are best avoided. Other customers may have double-dipped the cutlery in something you’re allergic to.
- Plan ahead when you travel: Tell the airline about your food allergies and order a special meal if you can. On trains and buses take your own food. Pack allergy medications in carry-on luggage in case of emergencies (plus spares in your suitcase). It’s sensible to carry both your prescription and a doctor’s letter; you may need to explain why you’re carrying meds. Breathing in food allergens is unlikely but you could pick them up on your hands from tables or armrests. So bring cleaning wipes. Translation cards or an app may help you identify allergens in a foreign country.
- Take care in the kitchen: Store food for someone with allergies on its own shelf and label containers. Clean surfaces, pots and pans, utensils and the microwave with a disposable wiper. Allergens can linger on sponges. Try always to eat at the table. And of course always wash your hands.
- At school: Create an allergy action plan with your child’s school or care provider. And make sure your child knows all the forms of food and drink their allergen could appear in. Give them the confidence to ask adults about a food if they’re in any doubt. And to ask for help if they start feeling unwell – including with vomiting or diarrhoea.
- Allergens exist in saliva too: Studies suggest that traces of peanut can linger in saliva for a few hours. So never share cutlery or drinking cups if you have food allergies. And at the risk of spoiling that first kiss, tell your date about your allergy first.
The best general rule is to wash your hands with soap and water before eating or putting your hands near your face. And any time you think you may have been in contact with allergens.
Is there a cure for food allergies?
You may be thinking of allergy immunotherapy. The idea is to reduce symptoms by gradually desensitising your immune system with repeated tiny doses of the allergen. It takes a long time and it’s not a cure. Food allergies can be trickier to treat this way than pollen or dust mite allergy because of the risk of a severe reaction. But oral immunotherapy is now available for peanut allergy from the age of four. The goal is to desensitise you to an accidental exposure to peanuts to help prevent a severe reaction.
Food allergy in children
Children may outgrow allergies to milk and other common early triggers such as eggs, soy and wheat. But peanut and tree nut allergy are more likely to stay with you into adulthood.
One way to help prevent food allergies starting in the first place may be to introduce babies to peanuts and other trigger foods much earlier. Allergy experts think starting from six months old might encourage the immune system to accept the allergens in later life. Talk to your GP or allergist first, especially if food allergy runs in your family or your baby has eczema (atopic dermatitis). Both make it more likely a child could develop food allergies.
Food allergies in adults
Your immune system goes on learning and adapting to new threats throughout your life. This means your allergy can change too. There’s a name for it – the allergic march. Just as kids can outgrow food allergies, grown-ups sometimes get them for the first time too.
The most common triggers for adults are shellfish and fish as well as peanuts and tree nuts. People having their first allergic reaction later in life often think it’s food poisoning. But you know now that vomiting and diarrhoea can be symptoms of food allergy too. So why not speak to your doctor just in case.