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Consuming or even coming into contact with certain foods can lead to unpleasant and sometimes dangerous physical reactions for some people. This is known as food hypersensitivity.
Food hypersensitivity includes food intolerance, which is when someone has difficulty digesting certain foods or ingredients in food. Food intolerance is not usually serious, but eating the food that they are intolerant to can make the person feel unwell. A person with a food intolerance may be able to eat small amounts of the offending food without any problems and may also be able to prevent a reaction; for example, if they have lactose intolerance, they may be able to drink lactose-free milk. Symptoms of a food intolerance usually develop a few hours after eating the food or ingredient that the person is intolerant to, and common symptoms include:
- Passing wind
- Tummy pain
- Feeling tired or exhausted
- Feeling sick
- Joint pain
These symptoms can last for a few hours or a few days. A food intolerance can cause some of the same signs and symptoms as a food allergy, so people can confuse the two, but food intolerances do not involve the body’s immune system – the body’s defence against foreign bodies – and do not cause anaphylaxis.
A food allergy, however, is a reaction involving the immune system. Proteins within foods can trigger immediate or delayed reactions and symptoms. Even small amounts of the offending food can trigger a range of symptoms, which can be severe or even life-threatening. Symptoms of a food allergy can affect any part of the body, including different parts of the body at the same time, and can, if severe, cause anaphylaxis. Common symptoms of a food allergy include:
- Feeling dizzy or light-headed
- Itchy skin or a raised rash (hives)
- Swelling of the lips, face and eyes (angioedema)
- Coughing, wheezing, breathlessness, noisy breathing or a hoarse voice
- Sneezing or an itchy, runny or blocked nose
- Feeling sick or being sick
- Tummy pain
The most common allergic foods include:
- Cows’ milk
- Peanuts, soybeans, peas and chickpeas
- Tree nuts, such as walnuts, almonds, hazelnuts, pecans, cashews, pistachios and Brazil nuts
- Shellfish, such as prawns, crab and lobster
However, a person can be allergic to any type of food, including celery, mustard, sesame seeds and lupin flour found in some baked goods.
Coeliac disease is a condition caused by an adverse reaction to gluten, where a person’s immune system attacks their own tissues when they eat gluten, which is a dietary protein found in three types of cereal:
Gluten is found in any food that contains those cereals, including:
- Breakfast cereals
- Most types of bread
- Certain types of sauces
- Some ready meals
- Some beers
Coeliac disease has some features of a true food allergy because it involves the immune system. Symptoms often include gastrointestinal issues as well as those unrelated to the digestive system, such as joint pain and headaches. However, people with coeliac disease are not at risk of anaphylaxis.
Food allergies affect between 1% and 2% of the UK adult population and 5%–8% of UK children. According to the Food Standards Agency an estimated two million people are living with a diagnosed food allergy, and 600,000 with coeliac disease.
How diet can influence allergy risk
Under normal circumstances our immune system reacts only when a substance is identified as a threat, such as when an individual is exposed to viruses, bacteria or foreign materials. However, in some cases, an allergic reaction occurs when our immune system mistakenly responds to a harmless substance, like proteins found in food, and treats it as a threat. The two key players in food allergy are allergens and antibodies.
Food allergens are proteins found in food which can cause a reaction in an allergic individual. There are often a number of allergens in foods responsible for food allergic reactions, for example there are at least 13 known allergenic proteins in peanuts.
Antibodies are responsible for detecting the allergen and presenting it to other cells in the immune system, which then leads to the symptoms of an allergic reaction. A particular type of antibody known as immunoglobulin E, or ‘IgE’, is most commonly responsible for allergic reactions to food.
The food we eat must be broken down before it can be absorbed and transported around the body to where it is needed. The digestibility of food can determine if food proteins will be tolerated in the body or not; cooked foods are more digestible than raw foods. It has been reported that partially digested food proteins may be recognised by the body as ‘invaders’ and an allergic response will likely develop.
Our knowledge about the causes of food allergy is still limited. However, it has been suggested that some nutrients may contribute to the development of food allergies such as:
- Vitamin D – this is an important regulator of an immune response. Scientists have proposed that both excess and low levels of vitamin D in the body, which are regulated by sun exposure and dietary intake of the vitamin, may increase the risk of food allergy.
- Omega-3 fatty acids – these regulate immune response and have an anti-inflammatory effect, protecting the cells from damage. Evidence suggests that omega-3 fatty acids intake has decreased and omega-6 fatty acids intake has increased from ancestral times. This imbalance leads to increased inflammation in the body and can potentially increase the risk of food allergies.
- Folate – this has been shown to affect immune function, so concerns have been raised on whether taking folate supplements during pregnancy and/or early childhood can increase the risk of developing food allergies. The scientific evidence to confirm this association is lacking and more studies need to be undertaken.
- Other nutrients – it has been reported that a maternal diet rich in foods containing antioxidants, i.e. vitamin C and copper, lowered the risk of developing food allergies in infants. However, vitamin and mineral supplementation may not have the same protective effect.
A person’s diet can affect their allergy risk and severity in a number of ways. Some foods may be more likely to cause inflammation; the most common allergic foods have been listed above.
How can diet choices help to prevent allergies?
Incorporating healthy foods into your diet can help to prevent allergies, for example:
- Yoghurt and foods with live cultures contain probiotics and “good bacteria” which have been shown to help regulate and strengthen your immune system, as “good bacteria” and flora in our bodies can affect our immune responses positively. Even though studies have not specifically targeted which probiotics and other “good bacteria” combat allergies, studies have shown probiotics may be a promising boost for allergy prevention and treatment.
- Apples – there may actually be something in the old saying “an apple a day keeps the doctor at bay”. An apple a day may actually help keep allergies away because apples are high in quercetin. Quercetin is found in other foods such as berries, capers, grapes, cabbage, cauliflower, onions, especially red onions, shallots, tea and tomatoes. Quercetin can help the body fight allergies because of its anti-inflammatory, antioxidant and antiviral properties.
- Omega-3 fatty acids – these are found in two common fish, tuna and salmon. The omega-3 fatty acids in these fish may help protect against inflammatory conditions such as allergies. Omega-3 fatty acids can also be found in walnuts and flaxseed.
- Turmeric – this is commonly thought to help with allergies because it contains curcumin. Research has shown curcumin can stop the production of some inflammatory molecules in mice. One study even suggests that humans might reduce allergic rhinitis symptoms with daily turmeric consumption.
- Honey – taking a teaspoon of honey is a common treatment for allergies, but don’t give honey to children under one year old.
- The vitamin C in oranges can enhance the immune system. Vitamin C is largely used to prevent the common cold, but the intake of all types of nutrients can also be used to strengthen the immune system against allergies. Other foods high in vitamin C include broccoli, strawberries and red peppers.
The theory behind all of these foods is that they may act as anti-inflammatory agents or antihistamines. However, there needs to be more allergy-targeted research to prove their effectiveness.
Why food choices matter: the impact of nutrition on allergy development
Generally, allergies are more common in children. However, a first-time occurrence can happen at any age, or recur after many years of remission. Evidence suggests that diet and nutrition play a key role in the development and severity of allergic diseases. A broad range of nutrients and dietary components are found to be effective in the prevention or treatment of allergic diseases through the suppression of type 2 inflammation, including:
- Vitamins A, D and E
- Minerals: zinc, iron and selenium
- Dietary fibre
- Fatty acids
- Phytochemicals such as those found in broccoli, cabbage, collard greens, kale, cauliflower and Brussels sprouts
The Western diet, which is low in fruits and vegetables and high in fat and sodium, is recognised as an environmental risk factor for developing allergic diseases. The Mediterranean diet, however, which includes lots of healthy foods such as whole grains, fruits, vegetables, seafood, beans, and nuts, has been found to be protective.
What factors determine if someone develops a food allergy?
It is still unknown why people develop allergies to food, although they often have other allergic conditions, such as asthma, hay fever and eczema. Most children who 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.
Another factor could be lack of vitamin D. Higher food allergy rates may be linked to the fact that we are spending more and more time indoors, depriving ourselves of vitamin D, which plays an important role in the development of the immunoregulatory mechanisms.
Other food allergy risk factors include:
- Family history – a person is at increased risk of food allergies if asthma, eczema, hives or allergies such as hay fever are common in their family. If both parents have allergies, children have a 60–80% risk of also developing one, compared to a 5–15% risk among children without allergic parents.
- Other allergies – if a person is already allergic to one food, they may be at increased risk of becoming allergic to another. Similarly, if they have other types of allergic reactions, such as hay fever or eczema, their risk of having a food allergy is greater. Infants with eczema are six times more likely to have an egg allergy and 11 times more likely to have a peanut allergy by 12 months than infants without eczema, according to a population-based study of one-year-old children in Melbourne, Australia.
- Age – food allergies are more common in children, especially toddlers and infants. As children grow older, their digestive systems mature and their bodies are less likely to absorb food or food components that trigger allergies. However, severe food allergies and allergies to nuts and shellfish are more likely to be lifelong.
- Asthma and food allergies commonly occur together. When they do, both food allergy and asthma symptoms are more likely to be severe.
Eating right for allergy prevention
Recent research is providing new insights into how it may be possible to prevent food allergies from developing in babies. European expert groups, in line with World Health Organization (WHO) guidelines, recommend exclusive breastfeeding, no solid foods or supplementary infant formula for the first four to six months of life. If breastfeeding for infants with a high risk of developing allergies is not possible, hypoallergenic formula should be used to reduce the likelihood of developing allergies.
Once diagnosed, the majority of food allergy diagnoses require complete avoidance of foods containing the allergen. However, 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.
Whether someone has one or multiple food allergies, their diet will be restricted in some shape or form, which puts them at risk for nutritional deficiencies. Nutrients are necessary for proper growth, development and good health at all stages of life. It is important to meet your nutritional needs with a balanced and diverse diet while avoiding your allergen(s). Generally, it is recommended to aim for a diet with the least amount of processed foods. The best way to replace those nutrients is to find safe food alternatives with similar nutrients. Look for nutrient-rich replacements in whole foods such as:
- Fruits and dried fruit such as apples, bananas, strawberries
- Vegetables such as leafy greens, potatoes
- Meat and poultry
- Grains such as barley, rice, oat, corn, rye, quinoa, amaranth, farina, excluding wheat
- Legumes such as lentils, peas, broad beans, chickpeas, soybeans, excluding peanuts
- Seeds such as pumpkin seeds, flax seeds, sesame seeds, poppy seeds, sunflower seeds
Eliminating major foods or food groups from your diet can have negative implications if the missing nutrients are not replaced.
Strategies for the prevention of allergy development
The best way to prevent an allergic reaction is to identify the food that causes the allergy and avoid it. Label reading is very important when managing food allergies. You will need to carefully read labels to make sure there are no allergens in the foods that you buy and/or eat.
It is helpful to obtain a ‘free-from list’ for the particular allergen that you wish to avoid from either a supermarket or a food manufacturer. They are available free of charge from the head office and/or websites of supermarkets or food manufacturers. They are regularly updated and usually include details of milk-free, egg-free, wheat-free, gluten-free, soya-free, tree nut- and peanut-free, sesame-free, preservative-free, vegan, vegetarian, etc. products.
Local health food shops will usually have a good selection of readily available special diet products. They will also have catalogues or websites that you can order products from that are not on the shelves.
By law all prepacked manufactured foods must declare the 14 main allergens in the ingredient list. Recent legislation, known as Natasha’s Law, has changed regarding prepacked food for direct sale too. This refers to food which is packaged at the same place it is offered or sold to consumers and is in packaging before it is ordered or selected. This must also list the 14 main allergens in the ingredient list.
When cooking at home, there are now plenty of allergy cookbooks on the market, often written by others with food allergies who want to share ideas and recipes. They are usually available from health food shops, bookshops, the internet, etc.
If you have already had a severe reaction from your food allergy, wear a medical alert bracelet or necklace that lets others know that you have a food allergy in case you have a reaction and you are unable to communicate.
If your child has a food allergy, take these precautions to ensure your child’s safety. Notify key people that your child has a food allergy. Talk with childcare providers, school personnel, parents of your child’s friends and other adults who regularly interact with your child. Emphasise that an allergic reaction can be life-threatening and requires immediate action. Make sure that your child also knows to ask for help right away if your child reacts to food.
If you suffer from a food allergy there are a number of charities, advice and support groups that can provide useful information including:
The Food Standards Agency – you can sign up for up-to-date food and allergy alerts.
Anaphylaxis UK – have created A Guide for the Food Service Industry – Protecting Allergic Customers.
Allergy UK – there is a dedicated Helpline 01322 619898 for people who need their help and support. They also provide free factsheets to explain the symptoms and triggers that people with allergies are dealing with every day of their lives.
Coeliac UK – for people who need to live without gluten.
British Dietetic Association – the BDA Food Allergy Specialist Group (FASG) is a group of dietitians working in adult and paediatric allergies.