Food Allergies FAQ's

There has been plenty of research into food allergy but, disappointingly, much of it has yielded conflicting results.

The lower rates of eczema, food allergy, asthma and allergic rhinitis in Third World countries lead experts to believe that the increase in allergies could be down to relatively recent changes in developed world lifestyles. There are a variety of theories that focus on genetics, epigenetics (the study of how genes can in some circumstances be altered by external factors), the environment, diet and infections.

But the frustrating answer is that we still don’t know.

These terms are often used interchangeably but they have distinct and specific meanings:

•  Food hypersensitivity is the umbrella term used to describe any reaction to food, encompassing both allergy and intolerance.

•  Food intolerance describes a reaction to substances other than food proteins that do not involve the body’s immune system. Many intolerances relate to a deficiency in specific enzymes which help digest certain foods. For example, lactose intolerance occurs when someone lacks the enzyme lactase and therefore can’t digest the naturally occurring sugar in milk called lactose.

•  Food allergy is the term reserved for reactions by the body’s immune system to food proteins. These reactions can be either immediate or delayed.

As the name suggests, these reactions happen quickly (within seconds or up to two hours after eating an allergen) and can, in some instances, be severe. They will result in one or more of the following symptoms:

• Skin (redness, eczema, hives, facial/ lip swelling)

• Gut (vomiting, diarrhoea)

• Respiratory tract (cough, wheeze, difficulty breathing, hoarseness, noisy breathing)

• Cardiovascular system (drop in blood pressure, profound drowsiness, lack of responsiveness or loss of consciousness)

• Anaphylaxis describes the most extreme form of an immediate allergic reaction where either difficulties breathing or a drop in blood pressure occur.

This is more difficult to diagnose as symptoms may occur one to three days after eating the relevant allergen. Some children are able to tolerate small amounts of the food protein but react to larger amounts, which can also complicate diagnosis. Typical symptoms can include one or more of the following:

• Eczema
• Vomiting
• Reflux
• Colic
• Abdominal pain
• Constipation
• Diarrhoea
• Blood or mucous in the stools
• Faltering growth

Additional symptoms such as lethargy, sleep disturbance and respiratory problems may relate to food allergies.

Immediate and delayed food allergic reactions are quite distinct. However, they are not mutually exclusive. It is increasingly common for an individual to have delayed reactions to one or more food allergens as well as immediate reactions to others.

Although any food protein has the potential to cause an allergic reaction, eight to ten foods account for 90 percent of all food allergic reactions. Eggs, cow’s milk and nuts cause the most immediate reactions followed by wheat, sesame, kiwi, fish, shellfish and soya. Fewer foods cause delayed allergic reactions with cow’s milk, soya, eggs and gluten causing the majority of problems.

Up to two-thirds of children with allergies react to more than one food with some children being allergic to three or more of the common food allergens. Some food allergies are more commonly associated with others. Allergy to tree nuts and sesame occurs more frequently in children with peanut allergy and soya allergy is more prevalent in children with cow’s milk allergy.

The good news is that about 80% of children who exhibit delayed reactions will grow out of their allergies by their third birthday. However, in a minority of cases, the symptoms can persist and should be thoroughly investigated. With immediate reactions, it depends on the allergen in question. Tolerance is usually acquired over time with the majority of children outgrowing their allergies to milk, egg, wheat and soya by their 10th birthday. Allergy to nuts, sesame, fish and shellfish tend to be more persistent, with only a minority achieving tolerance in childhood. At least 80% of children with nut allergy remain allergic in adult life.

Treatments for food allergy are still experimental and not ready for use outside of established research programmes. The best strategy is food allergen avoidance and the provision of an emergency care plan supported with appropriate medications.

Allergy tests are helpful in the diagnosis of immediate food allergy. They also help determine when to introduce foods into your child’s diet. Sometimes this will be done in hospital and sometimes it can be carefully managed at home following specific guidelines from your child’s allergy specialist.

Avoiding multiple food groups poses challenges. A trained dietitian should always be involved to ensure that the prescribed diet really is free from the relevant allergens and is nutritionally adequate.

However, the real experts are the parents who live, shop, teach and cook for their allergic children. I am thrilled that two such parents have taken the time and effort to pass on some of their invaluable experience, gleaned through years of living with allergy.

They have gone the extra mile in providing recipes that will suit 90% of all allergic children, with recipes free from eight common allergens. I am sure this will become a valuable resource for many families who face the daunting daily prospect of coping with food allergy.

The majority of food allergies present within the first two years of life as infants are introduced to new milk formulas and foods. The reactions can occur at any stage with some babies reacting within the first few weeks of life. Food allergic reactions occur when the body recognises a food protein as being ‘foreign’. This generates a strong immune response aimed at rejecting that food protein, leading to a range of symptoms affecting different parts of the body. Broadly speaking these immune-mediated reactions can be divided into immediate and delayed reactions.

Immediate reactions occur within minutes to two hours of eating the food. They can be provoked by minute quantities of food protein which binds to allergen specific IgE receptors in the body leading to the release of histamine and other inflammatory mediators. These reactions occur each and every time the food is given. Allergy tests (skin prick tests and IgE blood tests) are usually positive. The reactions can trigger a range of responses involving the skin, gut, respiratory and cardiovascular systems. Immediate redness and itching of the skin followed by the development of hives (urticaria) occur commonly. This can be accompanied by swelling of the lips, eyes, face hands and feet (angioedema). Vomiting also occurs frequently as the body attempts to rid itself of the allergen. Skin reactions usually resolve rapidly after withdrawal of the food allergen and respond well to treatment with antihistamine.

More severe reactions involve either the respiratory or cardiovascular systems. This may lead to the development of breathing difficulties with a persistent cough, wheeze, noisy breathing or voice change due to swelling of the airway. Alternatively, reactions may lead to a drop in blood pressure resulting in extreme pallor, floppiness, drowsiness or even collapse. These severe reactions are called ‘anaphylaxis’ and require immediate medical attention with the administration of injectable adrenaline.

Delayed reactions to foods are more insidious in onset and therefore more difficult to diagnose. The reactions typically occur within one to three days of eating the food leading to a range of symptoms affecting either the skin or gut. They usually require larger amounts of allergen to provoke a reaction. Allergy tests are usually negative. Typical symptoms can include one or more of the following: eczema, vomiting, reflux, colic, abdominal pain, constipation, diarrhoea, blood or mucous in the stools or faltering growth. Occasionally the vomiting can occur within minutes of eating and be severe and protracted leading to dehydration and collapse needing urgent medical attention. The term food proteinenterocolitis (FPIES) has been used to describe these reactions, which may be accompanied by bloody stools.

As many of these symptoms can occur in non-allergic infants it is often the co-association of features that makes the diagnosis more likely. Faltering growth is a worrying sign of possible malabsorption and requires urgent review. It is worth pointing out, however, that many babies with delayed food allergy have normal growth parameters.

Anyone of the 14 foods listed by the EU are capable of causing an immediate reaction. In the first two years of life, the main culprits are cow’s milk, eggs and nuts, which account for three-quarters of immediate reactions, followed by sesame, wheat, fish, soya, kiwi and, rarely, shellfish. Allergy to pulses (lentils, chickpeas, peas) occurs more frequently in Asian and vegan populations reflecting their higher consumption of these foods. Sulphites very rarely cause adverse reactions in infants.

The list of foods causing delayed reactions is shorter with four main food proteins causing most reactions. Cow’s milk causes the majority of delayed reactions followed by soya, gluten (wheat, barley, rye, oats) and lastly eggs. Approximately half of all infants with delayed reactions to cow’s milk also react to soya with similar symptoms.

Certain foods such as tomatoes and berries are high in natural histamines leading to mild rashes around the mouth post ingestion. Acidic foods such as pineapples and oranges can also aggravate the skin of a baby with eczema. These foods cause irritation as opposed to allergic reactions.

It is best to seek medical help early if you suspect that your child is food allergic. This not only ensures that an accurate diagnosis is made but also allows your child to progress with their weaning diet in a safe manner while ensuring that their diet is as nutritious and varied as possible. This usually requires the support of a children’s allergy doctor and dietitian. Although these recipes are free from 14 allergens, it would be foolish to avoid allergens if this was not necessary, so add in the appropriate suggested optional extras.

As allergists, once food allergy is diagnosed we would actively promote the early introduction and inclusion of a diverse range of ‘permitted foods’ while excluding a baby’s known allergens. In support of this approach, a recent study has found that including peanuts early into the diet of infants with eczema and egg allergy, significantly reduced the risk of having a peanut allergy at five years. In high-risk infants with eczema and/or other food allergies, allergy testing prior to introduction is recommended.

Testing food allergens can be carried out in infants from the age of three to four months and to inhalant allergens from the age of 12 months. Both skin prick tests and blood specific IgE tests are able to detect the presence of allergen specific IgE antibodies and this does not rely upon a prior history of food ingestion. The tests are very useful to diagnose or exclude immediate food allergy. They are also able to assess a child’s risk of reacting to a food not yet introduced. They are particularly useful in infants with moderate to severe eczema where the tests can help guide decisions regarding dietary elimination and inclusions. They do however require a skilled practitioner to interpret the tests in the light of the clinical history, as the tests are fraught with difficulty with both false positive and false negative reactions occurring. Food challenge tests are often needed where the diagnosis is still uncertain based on borderline test results.

There are no validated tests to diagnose delayed food allergy. Food Intolerance tests measuring IgE antibodies and other alternative tests have no role in the diagnosis of either immediate or delayed food allergy. The diagnosis of delayed allergy is made based on pattern recognition of symptoms followed by the implementation of a trial period of dietary elimination followed by challenge tests. In formula-fed infants with suspected cow’s milk allergy, a prescribed hypoallergenic milk formula may be offered for a trial period. In breastfed infants, a trial period of removing cow’s milk and soya from the maternal diet for four weeks may be suggested. Dietetic support and maternal calcium supplementation during such dietary implementation is important. Formula milks that are unsuitable for treating cow’s milk allergy in young infants include goat’s milk, lactose-free milk and soya milk in addition to most anti-reflux formulas which are based on cow’s milk protein.

Having one or both parents with either asthma, hayfever or eczema or a sibling with food allergy will increase an infant’s risk of food allergy. Being allergic to one food will also increase an infant’s chance of reacting to other foods, with two-thirds of those children being allergic to more than one food. Another high risk group are infants who develop persistent eczema within the first few months of life despite treatment with topical steroids and emollients. The risk rises with increasing eczema severity ranging between 30–60 per cent. These infants are also at greater risk of developing either asthma or hayfever in a progression known as ‘the atopic march’.

Ideally, these infants should be referred early for an allergy assessment and testing to inform on the weaning diet. If your baby is deemed to be high risk and is still waiting to be seen by a doctor, then it would be advisable to introduce foods of low allergenic potential first. When introducing foods that are capable of causing an allergic reaction, this needs to be done cautiously starting with a tiny amount of food touched to the inside of the lip, followed by small amounts of the food given at least an hour apart, in increasing incremental amounts over three days.

The immune systems of those allergic to dairy react to the proteins in the milk, which their bodies mistakenly interpret as harmful. Lactose intolerance is related to the carbohydrate in cow’s milk – lactose – and occurs due to a deficiency in the enzyme lactase which is needed to process lactose. There are two types of lactose intolerance: primary and secondary. With primary lactose intolerance, a reduction in the enzyme lactase occurs over time. Primary lactose intolerance is more common in African and Asian populations. Typically those with primary lactose intolerance cannot tolerate large amounts of normal pasteurised milk, but are able to tolerate cheese and yoghurt. Primary lactose intolerance presenting in infancy is rare and most infants having issues with dairy are likely to be diagnosed as being cow’s milk allergic, not lactose intolerant. Secondary lactose intolerance, is transient and occurs when a child has had diarrhoea for example after a gastro bug which may result in the temporary reduction of the enzyme lactase. This leads to the poor absorption of lactose when consumed. This is usually resolved after a couple of weeks of a low-lactose diet. Both forms of lactose intolerance are different from being allergic to dairy and do not involve the immune system.

Most products that are lactose-free still contain cow’s milk protein and are therefore not suitable for dairy allergy sufferers.