Key Points
- •
Infants most often develop food allergies in the order of exposure (e.g. milk, egg, fish, vegetables, etc.).
- •
The majority of infants and young children with food allergies have symptoms that affect at least two organs (cutaneous, gastrointestinal or respiratory).
- •
The most frequent allergic gastrointestinal reactions to food in infants and young children include colic, vomiting, diarrhea and failure to thrive. None of these is pathognomonic for allergy and may be caused by many other conditions.
- •
Food allergy should be suspected in cases of persistent severe symptoms, symptoms related to food intake, two or more different symptoms, two or more organ systems involved and allergic predisposition.
- •
Among children presenting with symptoms suggestive of food allergy, the diagnosis can be confirmed by controlled elimination/food challenge procedures in only about one third.
For the past decades, an increasing awareness of food allergy has emerged in western industrialized societies where confirmed food allergy seems to affect around 3% to 7% of young children and 3% to 5% of adults depending on population, methods and diagnostic criteria. However, the public perceives food allergy to be much more common. Given the public’s frequent misperception that various mild symptoms are caused by food-induced allergic reactions, performing a careful evaluation and correct diagnostic procedures is imperative to avoid over-diagnosis, which may lead to malnutrition, eating disorders and psychosocial problems, as well as family disruption. In contrast, under-diagnosis may result in unnecessary symptoms, growth failure and physical impairment.
True food allergies (i.e. immune-mediated reactions) are most often immunoglobulin E (IgE)-mediated reactions. However, non-IgE-mediated reactions may play a major role in delayed reactions. It is evident that a correct classification of an adverse reaction to foods will depend on the extent and the quality of the diagnostic tests and procedures performed.
No single laboratory test is diagnostic of food allergy. Therefore, the diagnosis has to be based on strict, well-defined food elimination and oral challenge procedures, preferably double-blind, placebo-controlled food challenges (DBPCFCs) in children older than 2–3 years and in cases of subjective symptoms. In infants, open, controlled challenges have been shown to be reliable when performed under professional observation in a hospital setting or a clinic. Food allergy is primarily a problem in infancy and early childhood. Most often the infants develop food allergies in the same order as the introduction of foods into the diet. Thus, the prevalence of reactions to different foods depends in part on the eating habits of a given population.
This review concentrates on gastrointestinal symptoms, which may cause suspicion of food allergy in early childhood, focussing on indications for food allergy evaluation. Specific disease entities, such as enterocolitis, proctocolitis, enteropathies and allergic eosinophilic esophagitis/gastroenterocolitis, are discussed in Chapters 44 and 45 .
Frequency
In prospective studies, the incidence of cow’s milk protein allergy (CMPA) during the first year of life has been estimated to be about 2% to 3% based on strict diagnostic criteria, as reviewed by Høst. Other common food allergens in children are egg, peanuts, tree nuts, soy, fish and cereal grains. The total cumulated incidence of food protein allergy during the first 3 to 5 years of life has been found to be about 4% to 7%. In a prospective birth cohort study, the point prevalence of food allergy at 3 years was 2.3%.
Adverse reactions to food additives have been demonstrated to affect less than 1% of unselected school children when using DBPCFCs. The most common positive reaction was worsening of atopic eczema and urticaria in atopic children. Among children with atopic symptoms referred to hospital allergy clinics, 23% were suspected of food additive intolerance. However, only 7% reacted to food additives on open challenge and only 2% had reproducible reactions when DBPCFCs were performed. Another study indicates that artificial colors and/or preservatives (sodium benzoate) in the diet may result in a dose-dependent increased hyperactivity in 3-year-old and 8–9-year-old children in the general population.
In children with symptoms suggestive of food allergy, it has been possible to confirm the diagnosis in only about one third by means of controlled elimination/challenge procedures.
Age at Onset of Symptoms
The age at which symptoms start depends on the time of introduction of the foods; infants frequently develop food allergies in the same order as that in which the foods have been introduced into the diet. Many prospective studies have demonstrated that symptoms in CMPA develop in early infancy, rarely after 12 months of age. The onset of disease is, in most cases, closely related to the time of introduction of cow’s milk-based formula. Allergy to hen’s egg is also more common in younger children, whereas allergies against peanut, tree nuts, fish and shellfish, fruit and fruit juice often have a later age of onset. In a Spanish study, this relationship between the age of introduction of various foods into the child’s diet and allergy to these foods was demonstrated ( Table 42-1 ).
| Age (Years) | Food |
|---|---|
| 0–1 | Milk, eggs |
| 1–2 | Peanuts, fish in Scandinavian countries |
| >2 | Fruits, legumes, vegetables |
| >3 | Pollen-related cross-reactivities (oral allergy syndrome) |
Clinical Features
The clinical features of food allergy in childhood are shown in Table 42-2 . In early infancy the most common food allergy is to cow’s milk protein. Similar to other food allergies, the majority have at least two symptoms and symptoms that affect at least two organ systems. About 50% to 70% have cutaneous symptoms; 50% to 60% gastrointestinal symptoms and about 20% to 30% respiratory symptoms. Also, approximately 0.5% of exclusively breastfed infants may react to food protein in their mother’s milk, and in these infants severe atopic eczema is the predominant symptom.
| CUTANEOUS REACTIONS | |
| IgE mediated | Urticaria, acute or chronic (rare) |
| Angioedema | |
| Atopic dermatitis | |
| Non-IgE mediated | Atopic dermatitis |
| Contact rash (e.g. perioral flare due to benzoic acid in citrus fruits) | |
| GASTROINTESTINAL REACTIONS | |
| IgE-mediated | Immediate gastrointestinal hypersensitivity (e.g. nausea, vomiting, diarrhea) |
| Oral allergy syndrome | |
| Colic | |
| Non-IgE-mediated | Allergic eosinophilic esophagitis, gastritis or gastroenterocolitis |
| Enterocolitis syndrome | |
| Dietary protein colitis | |
| Dietary protein enteropathy | |
| RESPIRATORY REACTIONS | |
| IgE-mediated | Rhinoconjunctivitis |
| Asthma (wheezing, cough) | |
| Laryngeal edema | |
| Food-dependent exercise-induced asthma | |
| Non-IgE-mediated | Pulmonary hemosiderosis (Heiner’s syndrome [rare]) |
| SYSTEMIC ANAPHYLAXIS | |
| IgE-mediated | Anaphylaxis |
| Food-dependent exercise-induced anaphylaxis | |
| OTHER REACTIONS | |
| IgE-mediated | Otitis media (secondary to allergic rhinitis and Eustachian tube dysfunction or an allergic middle ear inflammation) |
| Unknown mechanisms | Migraine (rare), arthritis (rare), Henoch-Schönlein purpura (rare) |
Symptoms occurring within a few minutes to 2 hours after food exposure (i.e. ‘immediate reactions’) are mostly IgE-mediated, whereas symptoms occurring more than 2 hours after food intake are classified as delayed reactions and are typically not IgE-mediated. Late reactions may occur after many hours even up to a few days, such as in allergic eosinophilic gastroenteritis. Delayed reactions are mostly non-IgE mediated. Anaphylaxis has been reported with varying frequencies, reflecting differences in patient selection. It is clear that patterns of reactions to foods may vary due to different exposure levels and different time intervals between exposures, as well as different thresholds of reaction.
Immediate IgE-mediated reactions to foods often involve two or more target organs, such as the gastrointestinal tract, the skin and the lungs, and may result in a variety of symptoms, including life-threatening reactions such as exacerbations of asthma, laryngeal edema and anaphylaxis with cardiovascular collapse. An exception is the food-pollen allergy , or oral allergy syndrome (OAS), a mucosal equivalent of urticaria, which is described in Chapter 46 . OAS is associated with allergic rhinoconjunctivitis and allergy to specific pollen, e.g. birch, ragweed and mugwort pollens, and is most often elicited by specific foods with pollen IgE cross-reacting with homologous proteins in fresh fruits or vegetables. After ingestion, pruritus and swelling in the mouth and oropharynx occurs, which may prompt the child to refuse the offending foods. However, in some cases OAS may progress to more severe reactions.
Gastrointestinal Problems in Early Childhood
Gastrointestinal manifestations of food allergy can be classified as a continuum from clearly IgE-mediated to mixed reactions dominated by eosinophilic granulocytes, to clearly non-IgE-mediated reactions. Immediate gastrointestinal hypersensitivity and oral allergy symptoms are mainly IgE-mediated; allergic eosinophilic esophagitis, allergic eosinophilic gastritis, and allergic eosinophilic gastroenterocolitis are mixed-IgE and non-IgE-mediated reactions, and food protein-induced enterocolitis, proctocolitis and enteropathy, and celiac disease are non-IgE mediated. The most frequent adverse reactions to food in the infant and young child are immediate IgE-mediated reactions with manifestations such as nausea, abdominal pain (colic) and vomiting within 1 to 2 hours after food intake, and diarrhea within 1 to 6 hours. The frequency of presenting gastrointestinal symptoms in infants with CMPA is shown in Table 42-3 .
| Symptom | SELECTED PATIENT SAMPLES (%) | UNSELECTED PATIENTS COHORTS, PROSPECTIVELY FOLLOWED FROM BIRTH (%) | ||||
|---|---|---|---|---|---|---|
| Goldman et al (1963) * | Gerrard et al (1967) † | Hill et al (1986) ‡ | Gerrard et al (1973) § | Jakobsson and Lindberg (1979) ‖ | Høst and Halken (1990) ¶ | |
| N = 89 | N = 150 | N = 100 | N = 59 | N = 20 | N = 39 | |
| Colic | 28 | 19 | 14 | 20 | 35 | 46 |
| Vomiting | 33 | 34 | 34 | 22 | 50 | 38 |
| Diarrhea | 37 | 47 | 48 | 41 | 25 | 8 |
| Failure to thrive | NG | NG | 22 | NG | 10 | 8 |
| Diarrhea with blood | NG | NG | 4 | NG | NG | 0 |
| Gastroesophageal reflux | NG | NG | 6 | NG | NG | NG |
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
