Food allergies in children

Allergy, hypersensitivity and the immune system

Food allergies are one form of food hypersensitivity. This is very important information, because not all the symptoms caused by food intolerance or hypersensitivity mean allergy. We speak of an allergy when the immune system is involved in the pathomechanism, i.e. the mechanism of symptom formation. This is known as immunological hypersensitivity. A large proportion of food allergies are related to immunoglobulin class E, or IgE It is about IgE-dependent reactions. But there are also IgE-independent reactions – and this is where a problem arises, because in principle we have no way of testing such allergies, or perhaps put another way, we are unable to document them.

Is pathomechanism relevant at all? In a sense, yes, because by knowing it, we can predict the development of the disease. However, if we consider the management of allergy – whether IgE-dependent, IgE-independent or mixed – in most cases it is the same. It is based on the use of so-called elimination diets. However, it seems that these diets are overused in Poland. They do not always need to be followed, or even if they do, not necessarily for as long as is often the case.

What do we know about food allergies in children?

Food allergies seem to affect a few per cent of people (estimated at 8% of children and 3.5-4% of the general population), although there is a lack of rigorous research to confirm this. So roughly one in 12 children may have such an allergy. More important than the epidemiology itself is that it is changing. Unfortunately, the number of patients with food allergy is increasing. This is due to various factors, including the fact that we have an increasing variety of foods, encountering more allergens.

The most common child allergens are cow’s milk proteins, followed by egg and peanuts. In older children, adolescents and young adults, it seems that peanuts start to dominate as allergens, as well as fish and seafood.

Food allergy most often affects children, especially in the first 2-3 years of life. Later on, of course, it is also present, but its prevalence definitely decreases in favour of other allergic diseases (this is the phenomenon of the so-called atopic march).

Main allergens

We have eight main groups of foods that sensitise us:

• cow’s milk proteins,
• hen’s egg,
• soybean,
• wheat,
• peanuts (they’re not nuts, they’re a species of plant in the broad bean family!),
• tree nuts (hazelnuts, walnuts, pecans),
• fish,
• seafood.

As many as 90% – or more – of food allergy symptoms are caused by these allergens. If we have any symptoms, these foods are the prime suspects.

Symptoms of food allergies can vary widely and come from many organs. They are not only from the gastrointestinal tract, but also from the skin, the respiratory system. Systemic reactions can also occur, such as anaphylaxis, which is one of the most dangerous manifestations of allergy – dangerous not only to health, but also to life. Contrary to common knowledge, unfortunately anaphylactic reactions – also after food, and in fact above all after food – also occur in children, even the youngest, i.e. infants.

Early onset. Food allergies in infants

In infants, the most common form of food allergy is IgE-independent allergy caused by cow’s milk proteins, which simply ‘does not come up’ in standard tests (whether skin tests or blood specific immunoglobulin determinations).

Inflammation of the prostate and rectum

IgE-independent allergy is usually associated with inflammation of the rectum and anus. Many parents have seen the characteristic symptoms of such inflammation – stools with an admixture of mucus or blood and reddening of the skin around the anus. The blood is in the form of veins or dots and is present in small amounts. There are no other symptoms (pains, colic). Some say they are happy babies who bleed a little. And this is indeed the case, as the development of these infants is going well, the babies feel well. Fortunately, these symptoms mostly pass on their own. Sometimes only an elimination diet needs to be applied for a short period of time, but as a rule it is enough to simply wait a while.

Inflammation of the small intestine and colon

Sometimes complaints can originate further down the gastrointestinal tract. Inflammation of the small intestine and colon gives both local and general symptoms:

• irritability,
• profuse sweating,
• vomiting after feeding – within 1-3 hours,
• abdominal bloating,
• stools mixed with blood,
• weight gain inhibition.

If the child is not gaining weight according to the centile charts, a red light should already be on for the parent. The most common causes of small intestinal and colitis are cow’s milk proteins and, less commonly, soya, cereals, rice and poultry. If it gives increased symptoms and lasts for a long time, it can lead to enteropathy, i.e. weight gain disorders combined with anaemia, hypoproteinaemia (protein deficiency) and hypocalcaemia (calcium deficiency). This is the point at which it is essential – and as soon as possible – to implement an elimination diet, because the child’s normal development is already at risk.

Allergic eosinophilic of eosophagitis, gastritis, enteritis

Two other forms of food allergy in children can also be identified:

• allergic eosinophilic oesophagitis
• allergic eosinophilic gastroenteritis.

These tend to occur in older children, but can start in early childhood. Typical symptoms are gastro-oesophageal reflux (nausea, vomiting, belching, heartburn), swallowing disorders, epigastric pain, especially after eating. To establish the diagnosis, an endoscopic examination must be performed – gastroscopy (stomach) or phagoscopy (oesophagus).

Food allergy in children – diagnosis

It is based on history and physical examination. We need to link the onset of symptoms and the contact with the food in question (i.e. the causative agent). The next step is the clinical examination – physical and additional examinations:

• skin tests,
• specific IgE (component diagnosis),
• eosinophilia determinations,
• basophil activation test.

It is important to remember, however, that the results of these tests are not decisive, but only guide to the correct diagnosis. The procedure that determines whether or not a food allergy is present is the provocation test. The provocation test is a requirement if a therapeutic elimination diet is to be introduced for a longer period of time.

Unfortunately, there is also no shortage of tests that are not recommended, unreliable and unreliable, but are nevertheless performed by patients. These include:

• IgE determination in tissues,
• antigen stimulation tests (CAST-ELISA),
• cytotoxicity evaluation,
• histamine release test,
• assessment of blastic transformation,
• determination of total IgG and IgG4 in serum.

Particularly popular are the latter tests, which do not show an allergy but only that the body has been in contact with the food in question.

For the diagnosis of cow’s milk protein allergy, the CoMiSS questionnaire is also sometimes used, which takes into account symptoms such as:

• crying,
• regurgitation (movement of food from the stomach into the oesophagus),
• stool appearance,
• skin symptoms,
• respiratory symptoms.

After completing the questionnaire, one is given a score. A score above 12 points indicates that an allergy may be suspected. But – again – this is only a suspicion. To be sure, a provocation test should be carried out.

Provocation test

The oral provocative test is performed after 2-4 weeks of the elimination diet (so-called diagnostic). This means that during this time the child does not receive the food in question, it is absolutely excluded from the diet. We then introduce a certain amount of this product and observe whether symptoms occur. Only when symptoms appear can an allergy to a particular product be diagnosed and an elimination diet applied for a longer period of time.

For how long? Experts’ opinions on this subject vary. Some say 6 months, others say 9-12. But always an elimination diet should have a definite duration, i.e. last until a certain point. It has been proven that unnecessarily following such a diet for a longer period of time (when the child has already acquired a tolerance) increases the risk of an anaphylactic reaction to that food later on.

For children with a cow’s milk protein allergy, milk mixtures with partial protein hydrolysis (HA) and soy formulas are also not recommended (as cross reactions often occur here).

Food allergies in children – risk factors

The risk of food allergies is increased by factors such as:

• delivery by caesarean section (altered bacterial flora, lack of protective bacteria from the birth canal),
• western diets (high intake of pro-inflammatory omega-6 polyunsaturated fatty acids – margarines, vegetable oils; reduced intake of soluble dietary fibre),
• race (more often black and yellow),
• vitamin D levels,
• intestinal dysbiosis,
• male gender.

Fortunately, food allergy can decrease with age. Tolerance is acquired. In most children, allergy symptoms disappear by the end of the 3rd year.

How to prevent food allergies in children?

Various attempts are made to counteract food allergies, but so far none are effective, and certainly there is no indication to delay the introduction of allergenic foods into the diet or to avoid allergenic foods, as was practised years ago.

Current recommendations include:

• avoiding the feeding of BMK-based modified milk in the first week of life in breastfed infants,
• introduction of boiled hen’s egg (not pasteurised or raw) during the period of expansion of the diet (between 4 and 6 months of age) as part of the prevention of hen’s egg allergy (1/3- 1/2 egg 2 times a week),
• introduction of peanuts (but not as the first complementary food) in the form of 1 teaspoon of diluted peanut butter.

NOT RECOMMENDED:

• the restriction of allergenic foods in pregnant and lactating women,
• the use of soya-based milk replacers in children under 6 months of age.

Based on ten years of observation, it has been proven that the more varied the infants’ diet, the lower the risk of food allergy.