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MikaelKuitunen

Food Allergy and Hypersensitivity in Children

Essentials

  • Food hypersensitivity refers to both food allergy and food intolerance. See picture 1.
  • Rapidly developing urticaria and angio-oedema are common symptoms of food allergy. It is typical that the symptoms recur or persist and that they are clearly associated with eating.
  • Atopic eczema should be distinguished from food allergy. Mild eczema is rarely associated with food allergy, but in an infant with severe eczema foodstuffs may aggravate the eczema.
  • Suspected food allergy is at least 6 times more common than food allergy confirmed by challenge testing.
  • Reddening of the skin, baby reflux, loose stools or stools of different colours, excessive crying and restlessness often occur in infancy. These are common, benign and transient symptoms, and an underlying food allergy is often suspected as the cause.
  • The assessment concerning nutritionally essential foods (milk, cereals) is performed by a specialist. Elimination trials with foods that only cause mild symptoms and that are easy to avoid (e.g. strawberry, tomato, citrus fruit) can be carried out at home under guidance from health care personnel. If the child has difficult cutaneous or gastrointestinal symptoms or if respiratory symptoms or anaphylaxis is suspected, he/she is referred to a specialist.
  • An elimination diet started in infancy should either be timely stopped (at the age of 2 to 4 years in most cases) or proper grounds must be given for its continuation.
  • Dietary requirements in children starting school are checked by the school nurse. A special diet is only indicated if there have been significant symptoms of food allergy in a fresh challenge test.

Epidemiology

  • As many as half of all parents with children aged less than 1-2 years associate some of their child's symptoms with food; however, the majority of these suspicions rapidly disappear, usually within 6 months.
  • In a survey of school children, 24% reported to have, or to have had at some stage, a food allergy. The prevalence of food allergy in childhood is 2-6%.
  • In food allergy, an immunological mechanism has been demonstrated in addition to the symptoms, either by determining food specific IgE antibodies in the serum or with a skin prick test.

Prevention

Aetiology

  • Any food that contains proteins can cause allergy. Genetic predisposition to allergies increases the risk. The environmental factors that increase the risk of allergy or that protect from developing allergy are not well known on the individual level.

Cow's milk, wheat and egg allergy

  • Milk, wheat and egg are important causative agents in infants and small children.
  • Rarely seen after pre-school age
  • Symptoms caused by these nutritionally important foods appear in infancy a few weeks after the food has been introduced to the child's diet.
  • The diagnosis should be confirmed with a supervised elimination-challenge test conducted in specialized health care.
  • See cow's milk allergy Cow's Milk Allergy.

Birch pollen allergy

  • Different plant allergens share a similar structure with birch pollen, and consequently, when eaten, many fresh fruits, vegetables and nuts cause itching of the lips, oral mucosa, throat and ears, as well as erythema and urticaria in the skin through direct contact in those with pollen allergy.
  • Tree nuts (e.g. hazel nuts and walnuts), peanuts (belonging to leguminous plantstogether with pea and soya) and almonds are common causes of symptoms. Raw root vegetables such as potato, carrot, celery and parsnip, and fruit with or without stone, such as apple, pear, peach, cherry, kiwi fruit, plum and mango, often cause symptoms. Spices can also cause symptoms, including mustard, caraway, turmeric, ginger and cinnamon. Many patients only get symptoms during the pollen season.
  • Preparation of fruit and vegetables (cooking and freezing) removes their allergenicity making it possible for those allergic to birch pollen to consume them.
  • Foods that cause symptoms are avoided according to symptom emergence. Due to cross-reactions, positive results are very common in skin prick and specific IgE antibody tests, but they correlate poorly with the symptoms. Therefore, testing is not recommended.

Food intolerance

  • Enzyme deficiency
    • The most common form is lactase deficiency, which leads to lactose intolerance. The symptoms usually emerge at school age or in adulthood.
  • Biogenic amines that release histamine
    • Strawberry, citrus fruit, chocolate, tomato

Anaphylactic reaction

  • In theory, any food can act as the causative agent.
    • In children: milk, wheat, egg, nuts, seeds
    • In adults: nuts, seeds, shellfish, and fish
      • The patient is referred to specialized care for further assessment and the reaction is appropriately recorded.

Essential questions

  • Signs and symptoms: what were the observed symptoms and when did they start, and have the symptoms recurred? What was the timing of the onset of symptoms in relation to food exposure? Strength of the symptoms?
  • Current diet; has some food already been eliminated and what are the reasons for the elimination?
  • Atopic eczema; what skin care methods have been used (moisturising lotions, emollients, topical glucocorticoids)?
  • Breastfeeding (duration of exclusive breastfeeding, total duration of breastfeeding), the first contact with infant formulas, introduction of complementary foods, any particular maternal diets
  • Family history of allergies
  • Smoking
  • Could the patient have a metabolic disorder, coeliac disease or lactose intolerance?Courses of antimicrobials (effect on intestinal symptoms)?
  • Growth chart (height, weight, head circumference)

Infant (< 1 year)

  • History
    • Do symptoms warrant further investigations or are they part of normal infancy? Infants are individual and their temperaments vary, which is reflected in the child's contentment, happiness, crying and sleep-wake pattern.
    • The consideration of confounding factors is particularly important.
    • Atopic eczema usually appears in infancy at the same time as new foods are tried, and the possibility of misinterpretation is great.
  • If a nutritionally essential or otherwise common foodstuff (cow's milk, cereals, egg) repeatedly causes significant and similar symptoms, it may be eliminated as a trial for a period of one week during which time the symptoms are followed. The matter should be investigated properly with the support of health care personnel.
  • Any food elimination that has no effect on the symptoms must be discontinued without delay.

An older child

  • Food-induced symptoms are unlikely
  • Cross reactions in birch pollen allergy: see above
  • A rash that heals in the summer is not caused by food allergy.

Symptoms of food allergy

Cutaneous manifestations

  • Urticaria and redness of the skin (immediate reactions), exacerbation of atopic eczema (delayed reaction and rarely the only symptom of food allergy)
  • Atopic dermatitis is a chronic inflammatory skin disease, and its underlying causes include heredity, environmental factors and disturbed penetration of the skin. A food substance is often found to be an exacerbating factor in severe atopic eczema in an infant.
  • Atopic dermatitis may be exacerbated by many factors, including dry winter air, stress, infections and sweating, as well as mechanical and chemical irritation. The relapsing-remitting nature of the disease is typical of the disease, which is challenging in infancy when many new foods are introduced.

Intestinal symptoms

  • Vomiting, changes in stool consistency, persistent crying and restlessness are very difficult to interpret in an infant. The frequency of bowel motions varies greatly between individuals. For example, a normal pattern for an infant may be a bowel movement 10 times a day or once a week (provided that the child is well and developing normally).
  • All changes in the diet can cause temporary changes in bowel function, which is a normal phenomenon.
  • Of gastrointestinal symptoms, the most obvious one is contact allergy around the mouth and lips which appears almost immediately after ingestion and is therefore easy to connect with the offending food (tomato, citrus fruit and apple in birch pollen allergy).

Respiratory tract symptoms

  • Rhinitis, itchy eyes, sneezing and dyspnoea are rare.
    • They are usually associated with a severe systemic reaction with signs of urticaria and anaphylaxis.

Symptom timing and other symptoms

  • IgE-mediated symptoms usually occur within minutes and no later than within 1-2 hours. Delayed symptoms occur within hours.
  • It is extremely difficult to associate delayed intestinal reactions, excessive crying, restlessness and exacerbations of atopic eczema with a particular food. A double-blind food challenge may be of use in the diagnosis.

Diagnosis of food allergy

  • Elimination and challenge tests form the basis of diagnosis (picture 2) Cow's Milk Allergy. For nutritionally important foods (milk and wheat in young children) an elimination-challenge test is carried out under physician supervision in specialized care or in the surgery e.g. according to the instructions below.
    • The suspected food(s) is totally eliminated from the diet (for 1-2 weeks).
    • The development/resolution of symptoms is recorded in a symptom diary.
    • Disappearance of symptoms supports the presence of food allergy, but it is not diagnostic. The food needs to be reintroduced.
    • A small amount of the food is introduced to the diet and as long as the child remains asymptomatic the amount is increased gradually to the normal (age-adjusted) daily amount. Find out about local challenge protocols. See also the article on cow's milk allergy Cow's Milk Allergy. Challenge of only a short duration is usually sufficient if, based on patient history, there is a suspicion that immediate symptoms such as urticaria and angio-oedema may appear. If delayed symptoms are suspected, the challenge is continued at home for a few days with the initially defined portions and then with age-appropriate portions until symptoms appear or the food is kept in the diet.
    • Immediate symptoms usually appear within minutes or within an hour. Delayed symptoms appear in 1-2 days following the reintroduction of the food (symptom diary), provided that the amounts consumed are adequate.
  • Tests of nutritionally less important foods that only cause mild symptoms can be carried out at home under parental supervision.
  • Suspicion of anaphylactic reactions caused by food: the situation is assessed in specialized care.

Allergy tests

  • IgE tests (specific IgE, skin prick tests) should not be used in the investigation of mild symptoms that are treated in the primary care.
  • In children with more severe symptoms, specific IgE tests targeted according to the patient history are carried out in specialized care.
  • IgE tests are not diagnostic.
  • As a basic rule, IgE testing of older children for foodstuffs should be avoided unless there is a strong suspicion or symptom.
  • Pre-school and older children can typically have positive results to skin prick and specific IgE tests, which are of no clinical significance.
  • Allergen component testing with IgE antibodies is a diagnostic method which is used to assess whether the child has cross reactivity with pollen proteins or a real nut allergy, and how severe is the allergy.
  • IgA and IgG antibodies only tell that the child has been in contact with the food in question and they are not useful in diagnostics.
  • Epicutaneous testing is according to current knowledge not a reliable diagnostic method.

Treatment

  • Food allergy is treated by avoiding the symptom-generating food for a specified period of time. The extent of avoidance depends on the severity of the symptoms; if the symptoms are mild there is no need to totally eliminate the offending food, which may hasten the development of tolerance. Otherwise, a normal age-appropriate diet is provided.
  • If nutritionally important foods (milk, cereals) are to be eliminated, it must be ensured that alternative nutrients are provided, and a dietitian should be involved in the care.
  • Normal growth and development of a child on a special diet has to be taken care of.
  • The majority of children with food allergy will experience accidental exposure to the offending food. The parents must be instructed to administer antihistamines as first aid for allergic reactions. If the child has had an anaphylactic or some other serious systemic reaction, he/she must carry an adrenaline auto-injector the use of which has been demonstrated http://www.dynamed.com/condition/immunoglobulin-e-ige-mediated-food-allergy#MEDICATIONS.
  • The mother to a child with food allergy can usually follow normal diet during breastfeeding.

Prognosis

  • Early childhood food allergies resolve quickly. Half of children with cow's milk allergy will tolerate milk at the age of 2 years and 75% at the age of 3 years. Cereal and egg allergies also resolve in the majority of children by the time they reach school age at the latest.

Follow-up and organisation of care

  • Individual foods which are of no nutritional significance can be eliminated in primary care if the causal relationship of food to symptoms is clear and the symptom is significant. Elimination and reintroduction can be carried out at home whilst keeping a symptom diary. Rechallenging is to be encouraged.
  • Clinical experience dictates the follow up routines.
  • Indications for a referral to a specialist
    • A small infant with widespread or worsening eczema
    • A small infant with difficult or perplexing symptoms, and the parents are convinced of food allergy
    • An infant in whom food allergy to an important nutrient is suspected (milk, wheat)
    • Failure to thrive
    • Barren diet
    • Suspicion of anaphylaxis
  • In primary care
    • The growth of a child on an elimination diet is monitored with growth charts.
    • Vaccinations are given according to the normal programme. Allergy to egg does not prevent vaccination unless the child has had an anaphylactic reaction to egg Vaccinations.
    • The family is encouraged to expand the diet towards a normal diet.
    • The child's diet should be regularly (annually) re-evaluated during the visits to the child health clinic: is the avoidance of certain foods based on an elimination-challenge test? Should a specialist re-evaluate the situation?
  • In Finland, one of the aims of the National allergy program (2008-2018) was to increase the tolerance of the population against allergens, and as a result, the number of special diets in daycare centres and schools was decreased by half http://www.jacionline.org/article/S0091-6749(21)00559-5/fulltext.

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Evidence Summaries ⬆