Food allergyT78.1

Frequently occurring, inflammatory, IgE-mediated or IgE-independent, local (gastrointestinal) or systemic reaction (e.g. urticaria, angioedema, asthma, rhinitis, etc.) to food itself or to food additives.

In contrast to this are the non-immunological food int olerances (NMU), the intolerances in the narrower sense (e.g. lactose intolerance, pseudoallergic reactions to salicylates, toxic or infectious causes, biogenic amines) or food intoxications.

It is not uncommon for food allergies to occur only in the presence of multiple co-factors:

• food + drug + alcohol
• food + drug + exertion (e.g. wheat-dependent exertion-induced anaphylaxis)
• Food + drug + systemic mastocytosis.

Food is responsible for 1/3 of all threatening anaphylactic reactions, in children even in 50% (Jäger L et al. 2001). In the USA, it is estimated that there are about 400 deaths/year. The most important causes are:

• Peanuts
• Tree nuts
• Fish
• Seafood
• Legumes
• Milk
• Hen's egg
• Seeds (linseed, sesame)
• Fruit (kiwi)
• Cereals.

Food allergies (NMA) can be divided into 4 groups and some subgroups according to pathogenetic aspects (see alsoFood allergens):

• IgE-mediated NMA
  • NMA type A
  • NMA Type B
  • NMA Type C
• Immunocomplex-related NMA
• Cytotoxic NMA
• T-cell mediated NMA (manifest clinically as eczema exacerbation in atopic dermatitis or as hematogenic contact dermatitis)

IgE-mediated food allergies are divided into 3 types according to Pichler:

• Type A (about 5-10% of patients): Occurs in infancy. Sensitization occurs via the gastrointestinal tract with relatively stable allergens. Proteins from milk (see below cow's milk allergy), egg, fish, peanut, hazelnut and soya are the most important allergens. As oral tolerance matures, the allergy (in about 80% of patients) recedes.
• Type B - or secondary food allergy (about 75%): Occurs in adolescents and adults. It is the most common form of allergy in Central Europe. Sensitization is via the respiratory tract (gastrointestinal tolerance is already more stable at this age!). Aerogenic allergens trigger the formation of IgE (e.g. pollen, latex), which cross-react with similar proteins in food. Patients usually have only mild symptoms, e.g. an oral allergy syndrome (see below allergy syndrome, oral = OAS).
• Type C - also primary food allergy (about 15% of patients): Primarily in "non-atopic" adult women who neither suffered from NMA in childhood nor were respiratory sensitized later. Sensitization occurs in the GI tract to relatively digestible proteins (e.g. chicken meat, crustaceans (see below crustacean allergy), fish (see below fish allergy), egg (see below hen's egg), milk (see below cow's milk) and various types of food. Meat (see meat allergy) as well as vegetable allergens like peanut, kiwi, fig, carrot and curry).

Incidence data vary considerably depending on the source. The subjectively perceived food intolerance is 20-30%.

In meta-analyses the following incidence figures of immunologically mediated food allergies are mentioned:

• 4.2% of children (relevant allergens: chicken protein, milk protein, soya, wheat and in recent years peanut; the frequency of peanut allergy has tripled in recent decades)
• 3.7% of adults (relevant allergens: wheat, celery, carrot, nuts, pome and stone fruit, crustaceans and shellfish).

Skin manifestations are common (50% of cases), possibly combined with allergic symptoms of the gastrointestinal tract and respiratory tract (about 20% of cases). Cardiovascular symptoms present in 10-15% of affected individuals.

After food ingestion, dysesthesias of the tongue are most commonly reported (35% of cases), followed by gastrointestinal symptoms (24%), erythema or pruritus (18%), urticaria (15%), rhinoconjunctivitis (12%), dyspnea (9%), eczema (6%), headache (5%), and anaphylaxis (0.3%).

Immediate type reactions due to food (according to Werfel):

• Mucocutaneous symptoms (most common):
  • oral allergy syndrome
  • urticaria
  • Angioedema
  • flush
  • pruritus
  • Lip swelling
  • Tongue swelling
• Eyes:
  • Itching
  • Redness
  • lacrimation
  • periorbital edema
• Gastrointestinal symptoms:
  • nausea
  • vomiting
  • Diarrhea
• Respiratory symptoms:
  • nasal congestion
  • rhinitis
  • Laryngeal edema
  • Hoarseness
  • bronchial allergic asthma
• Anaphylactic circulatory reaction.

Symptoms of delayed reaction or chronic exposure (var. n. Worm)

• Nausea
• Vomiting
• Abdominal pain
• Gastroesophageal reflux
• Inappetence
• Diarrhea
• Blood in stool
• Failure to thrive
• Food protein-induced enterocolitis syndrome in infants and young children (FPIES)
• Food protein-induced enteropathy in infants, young children and adults

Elicitation of the triggering substance by specific, precise anamnesis and, if necessary, record keeping.

Prickand scratch test of the suspected food with ready-made preparations or native (see also prick-to-prick test; atopy patch test).

Prick-block testing is performed if there is no specific indication for a possible sensitisation in the case of a suspected food allergy. The following are tested: apple, tree nuts, peanut, fish (cod), hen's egg, carrot, crustaceans (shrimps; only recommended for adults), milk, celery, sesame, soy, wheat.

Determination of specific IgE in the blood with CAP system or RAST. Here, in addition to the screening test, the single-cell allergens are tested.

Epicutaneous testing with native foods in infants has a high specificity and sensitivity, but is not yet a routine test in adults.

Testing by means of a targeted oral provocation test (gold standard: double-blind, placebo-controlled oral food provocation).

If necessary under stationary conditions:

• Oligo-allergenic diet (e.g. potato-rice diet in adults, extensively hydrolysed protein preparations in infants).
• Elimination diet (targeted omission of suspicious foods), at least for 7 days. In case of improvement, follow up with oral provocation.

Testing for dyes and preservatives first by capsule and then, under emergency conditions, by provocation testing through the original food.

Contraindication of provocation testing: life-threatening anaphylactic reactions in the anamnesis. Use of ß-blockers or ACE-inhibitors.

General information: In children, the results are only valid for 12 months, after which the test must be repeated. Patients must be free of symptoms at the time of testing and have sufficient time to take immunomodulatory medication: 3-5 days for systemic glucocorticoids or 5 days for systemic antihistamines.

Pseudoallergic reactions (additives, histamine intolerance)

Metabolic diseases (enzyme deficiency - e.g. lactose intolerance; fructose malabsorption)

Immunological diseases (e.g. celiac disease as gluten-sensitive enteropathy)

Intoxications (bacterial or other toxins e.g. phytoplankton [see below crustacean allergy])

Projection, aversion (most frequent differential diagnoses)

Therapy is based on the one hand on short-term (symptomatic) treatment of acute reactions, and on the other hand on long-term strategies to prevent the risk of recurrences (avoidance strategies with training and dietary programmes). New perspectives for achieving clinical tolerance seem to be offered by sublingual or oral immunizations.

Leave of absence: Apart from the emergency intervention for acute food allergy, the targeted (allergen) leave is the most important preventive element of a therapy. This requires a subtle and reliable diagnosis. This requires not only proof of sensitization, but also proof of clinical relevance. Here there is a need for professional advice (nutritionist). Special attention must be paid to allergens that lead to potentially severe anaphylactic reactions (see below food allergens)

Procedure after maternity leave: Recommendations for re-exposure after maternity leave are based on observations of the spontaneous course of the disease (see, for example, cow's milk allergy, chicken egg protein allergy, fish allergy, peanut allergy). It is particularly appropriate for children after 2 years of allergen-free periods under stationary surveillance.

Nutritional therapy: Due to the complexity of the individual sensitizations (heat-labile, heat-stable, cross-reactions (see also lipid transfer proteins), type of immunological response), a detailed dietary plan with avoidance strategy and advice on a sensible use of nutrition is absolutely necessary.

If necessary, emergency drug therapy according to the stages of anaphylactic shock. S.u. shock, anaphylactic.

Specific immunotherapy: As the study situation for immunotherapy in pollen-associated food allergies (e.g. immunotherapy for birch pollen-associated apple allergy) is unclear, immunotherapy is only recommended if allergic respiratory symptoms are present at the same time.

• Acute therapy: In acute type I symptoms, therapy according to the stages of anaphylactic shock. See below Shock, anaphylactic.
• In food allergies where the allergen is difficult to avoid (e.g. milk, wheat), prophylactic administration of disodium cromoglicic acid (e.g. Colimune) may be given. Adults and adolescents receive 200 mg 4x/day as permanent medication.

• Data on the course show that early childhood milk protein allergy has a good prognosis in terms of spontaneous tolerance development. This natural course is also observed with other allergens. It is strongly dependent on the food source. In addition to cow's milk allergy, allergic patients to chicken protein, wheat and soy tend to experience spontaneous remission in the first years of life.
• Peanut and tree nut, fish and crustacean allergies persist into adulthood.
• High specific IgE levels often correlate with clinical relevance and rarely tend to develop tolerance.
• IgE antibodies to food allergens may rise or fall during the course. The drop is often associated with tolerance development.
• Food allergies in adulthood may represent persistence of a childhood form or be a de novo development.
• For preventive measures see below. Allergy prevention.

• Lifelong avoidance of the triggering substance. In cases of confirmed food allergy, the targeted elimination diet is the only intervention whose effect has been proven to be effective. In some cases, the food is tolerated again after several months of abstinence, but in type I reactions, renewed provocations are always associated with a risk. Peanut (usually a lifelong allergen) is the most common cause of severe to fatal anaphylactic reactions. Fish allergens also have a pronounced allergenicity (aerogenic transmission!).
• Fruit sensitization is frequently coupled with pollen allergies. Specific immunotherapy against pollen allergens is accompanied by an improvement in food tolerance in the majority of cases. Specific immunotherapies directly with food (e.g. peanuts, hazelnuts) have so far had many side effects and need to be further investigated in controlled long-term studies.

• Notice. The legal directive (Directive 2003/89/EC amending Directive 2000/13/EC of 25.11.2003 and the update of 22.12.2006) defines allergenic foods that are subject to declaration.

• The declaration is obligatory for eggs, peanuts, fish, crustaceans, lupine, milk (incl. lactose), nuts (hazelnuts, almonds, etc.), molluscs (mussels, squid), celery, mustard, sesame seeds, soy, sulphur dioxide and sulphite from 10 mg/kg food, cereals containing gluten.
• Instead of the usual class names (e.g. vegetable oil, fruits, spices, vegetables or natural flavourings), the individual ingredients must be listed in future if the food class accounts for more than 2% of the product or if it contains ingredients from the above-mentioned list. However, these regulations do not apply to loose, unpacked products.
• Heating can eliminate some allergens. Allergens of animal origin tend to be thermostable, while plant allergens tend to be thermolabile.
• Patients with anaphylactic reactions with respiratory and circulatory involvement, those with a clearly defined trigger that cannot be completely avoided, and those with a greatly increased risk of developing anaphylaxis (e.g. Adults with mastocytosis, children with high peanut sensitisation) should carry an emergency kit containing an antihistamine (e.g. Fenistil drops), a systemic glucocorticoid (e.g. Celestamine 0.5 liquidum) and an adrenaline autoinjector as a precaution.

Common food allergens in Germany

Food additives and their E-numbers (food allergy)

Thermolability of food

Supplementary food should be given to children with an increased risk of allergy between the 5th and 7th month of life, including the feeding of more allergenic foods. Then the chance of tolerance development is higher. Full breastfeeding for 4 months is recommended for this risk group, although longer breastfeeding is not harmful.

In recent years, there is increasing evidence that food allergies can also be acquired through the skin (Tamagawa-Mineoka R et al. 2018). For example, patients who used soaps containing oat and almond relatives developed dysphagia and diarrhea after consuming foods containing cereals. A similar situation has been reported with corn products (soaps).

• 55-year-old female patient with 5 years of allergic rhinoconjunctivitis during the spring months. Proven sensitization to birch, alder and hazel pollen (see below tree pollen). A specific immunotherapy (hyposensitization therapy) with tree pollen carried out over 4 years led to a complete improvement of the clinical symptoms.
• Recently itching of the oral mucosa when eating hazelnuts. Testing: Prick test with a commercial hazelnut extract and prick-to-prick test with raw hazelnuts positive. Detection of specific IgE on hazelnut ( RAST class 3).
• Double-blind placebo-controlled provocation with hazelnut: Tingling with swelling of the lips and tongue when a hazelnut pudding is taken. 4 hours later severe rhinoconjunctivitis persisting for 24 hours.
• Dg. Oral allergy syndrome to hazelnut.

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