food allergies

5/21/2018 Food Allergies

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Food Allergies, Food Intolerance, and Skin Disorders

I. Definition1. Allergyan adverse reaction following exposure to an inhaled, ingested, or injected substance that resu

in a response from the immune systema.Asymptomatic allergya person who produces antibodies without having any symptomsb.Symptomatic allergya person who produces antibodies and has symptoms

2. Food allergyan adverse food reaction that is mediated by an immunoglobulin E (IgE) immunologicmechanism; induced by cell-mediated or immune-complex disease; the reaction occurs consistently afteingestion, inhalation, or touch of a particular food causing functional changes in target organs-an immune response, generally from IgE, which usually occurs within 2 hours. A food allergy results frohypersensitivity to an antigen of food source (usually protein). The manifestations of the allergy are causby the release of histamine and serotonin. The most common results (70%) of food allergies aregastrointestinal: diarrhea, nausea, comiting, cramoing, abdominal distention and pain; 24% are skin rela4% are respiratory, and 2% involve other systemic responses

3. Food intolerance*an adverse reaction to a food caused by toxic, pharmacologic, metabolic, or idiosyncratic reaction to the

foods or chemical substances in the food*a physiologic response to an ingested food or food additive that is not proved to be immunologic in natuThis category includes idiosyncratic, pharmacologic, metabolic, or toxic food reactions

4. Food idiosyncrasya quantitatively abnormal response to a food or food additive. Such response differsphysiologic or pharmacologic effect and resembles a hypersensitivity reaction, but there is no immunemechanism

5. Immune systemall organs, cells, and molecules that respond (both positively and negatively) toenvironmental substances

6. Immunoglobulin E (IgE)-mediated reactionrapid onset of symptoms occurring after ingestion of a specallergen that cross-links the antigen-specific IgE molecule to mast cells and basophils7. Pharmacologic food reactiona reaction to chemicals, including food additives, ingested food8. Antigensusually a foreign substance (e.g. protein, cells, bacteria, polysaccharides) that stimulates

antibody production

9. Allergensubstance foreign to the body that on interaction with the immune system, causes an allergicreaction

10. Mast cellstissue cells that release histamine or other substances causing allergic symptomsII. Objectives of Dietary Management

1. Exclude or avoid the offending allergen. If it is not known, use the Rowe elimination diet to discover caus2. Monitor the onset of the reaction, which may be delayed or immediate, If delayed, the onset of the reacti

may take as long as 5 days. An immediate response is more common with raw foods; patient history mainclude diarrhea, urticarial, eczema, rhinitis, and asthma. Cooking may alleviate some allergic propertiesbut this is not guaranteed.

3. Treat nutritional deficiencies or ensure adequate supplementation4. For patients with asthma, use a normal diet with small meals. Nothing should be given after dinner, to

reduce GI reflux.


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5. Keep food diaries to determine food reactions.6. Ensure intensive nutritional counseling when allergies are complex to avoid nutrient deficiencies and

unnecessary restrictions

III. Immunologic Basis for Allergic ReactionsThere are many adverse reactions to the ingestion of food including allergic, idiosyncratic, toxic, metaboand pharmacologic reactions. Food allergy can be distinguished from other types of adverse reactions tofood by the following features:

a.It is mediated by an immunologic mechanismb.It can be consistently reproduced by a blinded food challengec.It causes functional changes in the target organ

IV. The Immune SystemFunction: it clears the body of foreign substances or antigens (e.g. viruses, bacteria, blood cells, and tissuecells)

The immune system consists of the bone marrow, bursal-equivalent tissue, thymus, spleen, lymph nodetonsils, gut-associated lymphoid tissues (Peyers patches) and bronchial-associated lymphoid tissue (Lusterpatches).

3 type of cells that respond to antigens:1. B lymphocytesthese produce antigen-specific antibodies in response to an antigen2. T lymphocytesthese do not produce antibodies but recognize antigens3. Macrophagesthese are derived from monocytes in the blood; through phagocytosis, the macrophage

engulfs and destroys antigens

2 branches of the immune system:1. Cellular or cell-meditated pathway

This involves the actions of T lymphocytes (T cells) produced by the thymus. The T cells produclymphokines and cytokines (substances that regulate the activity of the B cells) causing direct cellulardamage to target cells and destroying the antigens. T cells generally protect against tumors and help or

suppress immunoglobulin production. The cells may play a role in gluten-sensitive enteropathy.

2. Humoral mediated responsesHumoral immunity involves antibodies (immunoglobulins) which have an important role in food

allergy. The B cells are produced by bursal-equivalent tissue. In response to an antigen, B cells producethe immunoglobulins (antibodies) IgA, IgD, IgE, IgG, and IgM that bind the antigens. This leads toneutralization, osponization, complement activation, phagocytosis, or hypersentivitiy reactions. IgD, IgGand IgM protect against bacteria. IgA in the saliva and intestinal secretions prevents absorption ofmacromolecules. IgE attacks parasites and is the immunoglobulin responsible for the classic allergicreaction.

The thymus and tonsils have a role in immunity*The thymus (a ductless, glandlike organ that produces T cells) is important in the development ofperipheral lymphoid tissue*The tonsils (two small, rounded masses of lymphoid tissue found along the path of inspired air andingested food and liquid) trap foreign materials inspired into the airways in the tonsillar crypts that come contact with antigen-processing cells

Types of allergic reactions

Reaction/Classification Mechanism Comments

Type I: immediatehypersensitivity,

Allergen binds with sensitized IgE antibodyon mast cells (specialized granular cells in

Applies to hay fever, anaphylaxis, most foodallergies, atopic dermatitis, asthma. Symptom


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Reaction/Classification Mechanism Comments

anaphylactic the intestines, skin, and respiratory tract) orbasophils (similar to the cells in blood). Thisresults in the release of mediators(histamine, eosinophilic chemotactic factor,bradykinin, etc.) IgG has also been identifiedas being involved in this reaction.

occur within seconds to up to 2 hours.Symptoms of food reactions may includelaryngeal edema, nausea, vomiting, severeabdominal pain, bloating, diarrhea, andio-edema, eczema, erythema, itching, hoarsenewheezing, cough, chest tightness, hypotensiobroncho-spasms, and shock

Type II: cytotoxic IgG antibody reacts with cell membrane oran antigen associated with the cellmembrane

Results from transfusion of incompatible blootypes.No food reactions have been demonstrated

Type III: Antigen-antibody complex Anthusreaction

Antigen and antibodies (IgG and IgM) form acomplex called precipitating antibody. Theantigen-antibody complex is known asArthus reaction when it occurs in softtissues, like blood vessels, lungs, or kidneysand as serum sickness when the complexcirculates. Complement is also activated insome cases.

Occurs in some food reactions. Milk precipitinhave been found in the lungs of some childrewith chronic respiratory infection and in the Gtract of those with gastro-enteropathy.Reactions usually take 6 hours or more toappear and may take several days to beclinically apparent

Type IV: delayed or cell-mediated hypersensitivity

T cells interact directly with antigen Usual mechanism of graft rejection. Possibleinvolved in some food allergies, such as protlosing enteropathies

V. Pathogenesis of Food SensitivityType I IgE mediated reactions occur most frequently. Sensitized IgE binds to mast cells, specialized granulacells, in the respiratory tract, skin and intestines. An allergic reaction occurs when an allergen bridges twomolecules of sensitized IgE, causing the cell to release chemical mediators (including histamine) and the celmembrane to release phospholipids. The mediators cause itching, contraction of smooth muscles, dilation ofsmall blood vessels, secretion of mucus, and attraction of eosinophils to the area.

VI. Common Food Allergens1. Foods most commonly reported to cause allergic reations in the pediatric population are cows milk,

chicken eggs, legumes (peanuts and soybeans), wheat, tree nuts (filberts and cashews), and fish. Studiein adults are limited, but they indicate that shellfish, peanuts, nuts and grains frequently cause reactions

2. Cross-reactivity may occur between different foods especially between foods in the same biological famiFor example, patients allergic to soybeans are often allergic to other legumes.

3. Allergens are usually acidic proteins or glycoproteins. Antigenic activity is believed to reside in a specificseries of amino acids that binds with the IgE antibody. The amino acids may be sequential or linear in thprotein molecule, or they may be brought into correct sequence by folding of the protein molecule.

Most common allergens and nutritional consequences

Milk Check for deficiencies in protein, riboflavin, vitamin A,vitamin D, and calcium. Be wary of introduction of cows min infancy

Eggs Check for iron deficiency. Egg albumin is used inmarshmallows, frozen dinners, and many other food mixeYolks are generally tolerated

Wheat Check for B vitamins and iron. Read labels on packagedsoups, sauces


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Fish Soiled sources, even before taste change occurs, areespecially high in histamine

Shellfish (crab, lobster, shrimp) Severe reactions may occur

Tomatoes Usually an allergenic reaction to tomatoes is linked to thefrequency of use in the diet

Citrus fruits Person allergic to citrus fruits can easily become deficienvitamin C. A supplemental source may be needed

Cola, chocolate These are easily identified in foods

Legumes (peanuts, soybeans, peas, lima beans) Watch labels for lecithin and other soy additivesCorn Hidden sources of corn include cornstarch, corn syrup, co

oil, frozen yogurt, baking powder, paper plates, etc

Nuts Avoid nut butters also. Aflatoxin can cause reactionSpices Cinnamon is a common allergen

Artificial food dyes It may be necessary to eliminate aspirin and salicylates.Many drugs contain tartrazine (FD&C no. 5 yellow dye).

Molds This category include penicillin. Use a diet low in milk andmilk products (watch out for deficiencies in calcium andriboflavin), mushrooms, cheese, sour cream, bacon, jamsand jellies, spices and sausages

Sulfites Foods from sald bars, wine, beers, colas, dried fruits andvegetables, maraschino cherries, dried or frozen potatoesmay contain sulfites

VII. Food Allergy SymptomsSymptoms of IgE-mediated food allergy can occur within seconds or up to 2 hours after eating a food(immediate reaction). In immediate hypersensitivity reactions, symptoms may not occur for several hours whdelayed reactions occur 2 to 48 hours after.

The common results (70%) of food allergies are gastrointestinal; 25% of results are skin-related, 4% arerespiratory, and 2% involve other systemic responses.

Symptoms of Food AllergiesGastrointestinal ManifestationsAbdominal painNauseaVomitingDiarrheaGI bleedingProtein-losing enteropathyOral and pharyngeal pruritus

Cutaneous ManifestationsUrticaria (hives)AngioedemaEczemaErythema (skin inflammation)ItchingFlushing

Respiratory ManifestationsRhinitisAsthmaCoughLaryngeal edemaMilk-induced syndrome with respiratory disease(Heiners syndrome)Airway tightening

Systemic ManifestationsAnaphylaxisHypotensionDysrhythmias

Controversial or Unproven ManifestationsBehavioral disordersTension-fatigue syndrome


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Controversial or Unproven ManifestationsAttention-deficit and hyperactivity disorder (ADHD)Otitis mediaPsychiatric disordersNeurologic disorders Neurologic disordersMusculoskeletal disordersMigraine headaches

VIII. Diagnosis of Food AllergyIn no instance do the results of a single test determine a conclusive diagnosis of food allergy. Its

diagnosis is based on accumulated evidence that includes the history, physical examination, appropriateimmunological and other tests, trial elimination diet, and food challenge.

Food Allergy Assessments

Aspect Description

History *provides a detailed description of symptoms, time from time of ingestion of footo onset of symptoms, most recent reaction, and quantity of food necessary toproduce a reaction, and suspected foods*includes family history of allergic disease, enzyme deficiencies and so forth

Physical examination *includes anthropometric evaluation, assessment of growth and development anutritional status*assesses other chronic diseases*evaluates allergic conditions like allergic rhinitis, eczema, and asthma

Food and symptoms diary for 2 weeks *provides actual record of food, amount and time when eaten, time of appearanof symptoms and any medication taken*allows assessment of dietary adequacy

Immunological testing (skin tests,RAST, others)

*yields of suspect foods*requires confirmation of positive results by trial elimination diet and foodchallenge to show clinical sensitivity to food

Trial elimination diet for 2-4 weeks or

until symptoms clear

*needs to be nutritionally sound

*required that patient record all ingested food as the suspect food may beingested in an alternative form*begins with a simple elimination diet; only foods suspected by history, food diaand/or immunological testing are eliminated*progress to more extensive elimination diet if symptoms do not clear on simplediet. Only one food in each food group or exotic foods never eaten before areallowed*may require use of hypoallergenic diet if symptoms do not clear on an extensivelimination diet

Food challenge *excludes foods known to cause severe reactions such as wheezing, asthma, oanaphylaxis

*return suspect foods to diet one at a time after symptoms have cleared for 2weeks. The amount is increased until it approximates usual intake.*is repeated following positive reactions as coincident reactions are common*performed as double-blind challenge when uncertainty about reaction persists

Diagnosis of Food SensitivityReliable Tests

Oral Challenge The patient is on a hypoallergenic diet and given a test doof suspected food in capsule form and response ismeasured. The test may be open, blind, or double blind.


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Skin Testing Dilute extract of food is placed on scratched or puncturedskin. This test is more accurate for nonfood allergies (polletc.) and needs follow up by oral challenge as there aremany false positives for food allergies

ELISA (Enzyme-Linked Immuno-sorbent Assay) This test is similar to RAST but does not use a radioactivsubstance. It is also less expensive.

Unreliable Tests

Cytotoxic Testing (Leukocyte Antigen Testing, Brians Test) White blood cells are mixed with plasma and examined

under a microscope with exposure to a food sampleNeutralization Testing (Provocative Testing) Food extract is injected under the skin to cause symptom

which are followed by more injections to neutralizesymptoms

Sublingual Testing Drops of food are placed under the tongue and symptomare recorded

Food Intolerance*a non-immune reaction to food or food additives*its symptoms include gastrointestinal, cutaneous, and respiratory disorders often similar to food allergy

Food additives (preservatives, flavor enhancers, coloring agents)1. Aspartamea nutritive artificial sweetener

*WHO and FDA maximum level of acceptable intake is 40-50mg/kg BW*Symptoms: headache, rash, leg nodules

2. Benzoates and Parabensextreme reactions rarea. Benzoic acid (sodium benzoate)most common antimicrobial food additive or preservative in

carbonated and non-carbonated beverages, syrups, fruit salads, icings, jams, jellies, preserves, saltmargarine, minced meat, pickles and relishes, sauerkraut, pie and pastry fillings, and cider

b. Parabenspreservatives and antimicrobial agents*later stages of paraben metabolism mimic the metabolism of benzoates*terms of food labels include methyl p-hydroxybenzoate or propyl p-hydroxybenzoate*added to processed vegetables, baked goods, fats and oils, and seasonings, cakes, pie crusts,pastries, icings, toppings and fillings (fruit jellies and creams), ciders, carbonated beverages and beefruit products (sauces, juices, salads, syrups, fillings, preserves and jellies), sucrose syrup, olives, anpickles

3. Butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT)antioxidants used to inhibit fat oxidat*used in vegetable oild and shortenings for deep-fat frying; found in high fat foods such as potato chnut meats, doughnuts, pastries and pie crusts; dehydrated potatoes, dried fruits, breakfast cereals acake mixes; terpene-like flavoring, oils (orange, lemon), chewing gum, candy, and yeast

*Symptoms: chronic urticarial

4. Mold*symptoms: when ihaled, include allergic rhinitis (sneezing, running nose, congestion and itchy eye a

nose); wheezing; difficulty of breathing*Avoid mushrooms, cheese, sour cream, buttermilk, bacon, sausage, and ham

5. Monosodium Glutamate (MSG)widely used food additive and flavor-enhancer to canned, packaged andprepared foods, commercial spice mixtures, bouillon cubes, hydrolyzed protein


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*Symptoms: Chinese Restaurant Syndrome; headache, tightness of chest, stiffness and/orgeneralized weakness of the limbs, light-headedness, facial flushing, profuse sweating,heartburn,gastric discomfort, and burning sensation at the back of the neck

6. Nickel or nickel salts*Symptoms: dermatitis, eczema*Foods to avoid in a nickel-restricted diet1. Meat: shellfish (shrimp and mussels)

2. Vegetables: beans (green, brown, white), sprouts, kale, leeks, lettuce, peas, spinach3. Fruits: figs, pineapple, prunes, raspberries4. Grains: buckwheat, millet, oatmeal, wheat bran products, multigrain bread5. Drinks: chocolate and cocoa drinks, tea from dispensers

7. Nitrates and nitritescommonly used preservatives and known for their flavoring and coloring attributes*Symptoms: vascular headaches, associated with increased incidence of certain cancers*Avoid: cured or processed meats such as ham, bacon, salami; listed on the ingredient label as sodnitrite or potassium nitrite

8. Penicillin*Symptoms: some types of chronic urticarial or allergies attributable to penicillin*Avoid: milk and all dairy products, cheese and cheese products, cream and cream products, milksolids, casein, lactalbumin, curds, whey since they may conain penicillin as a contaminant

9. Sulfites and sulfating agentsused to prevent browning, modify dough texture, control microbial growth, andcertain bleaching foods

*Symptoms: bronchospasms (asthmatics); reported but not proven symptoms include flushing, hivesGI disturbance, anaphylactic shock

Foods to avoid:1. Bakery products: cookies, crackers, pie crusts, pizza crusts, quiche crusts, flour tortillas, all baker

products with dried fruits and vegetables2. Beverage: beer, cocktail mixes, dried citrus fruit, beverage mixes, wine, wine coolers3. Dairy products: filled milk (skim milk enriched in fat content with vegetable oil)4. Fish and shellfish: canned clams; dried cod; fresh, frozen, canned and dried shrimp, frozen lobstescallops5. Fruits: processed fruits including canned, bottled or frozen fruit juices; dried fruit; canned, bottled,frozen diuretic fruit or fruit juices, maraschino cherries, glazed fruits 6. Vegetables: fresh, pre-cut potatoes7. Others: condiments and relishes (horseradish, onion and pickle relish, pickles, olives, salad dressmixes, wine vinegar)8. Sweets: confections and frosting containing brown, raw, powdered or white sugar derived from su

beets

10.Tartrazine and Acetylsalicylic Acid*Tartrazine (FD and C yellow No. 5) coloring dye used in foods, drugs, and cosmetics*Acetylsalicylic acid (aspirin): the only proven allergenic salicylate*Symptoms: chronic urticarial, asthma

Carbohydrate intolerancethe most common enzyme deficiency*a deficiency of the intestinal enzyme lactase results in a decreased ability to digest lactose, the sugar in milk;

symptoms of abdominal cramping, flatulence, and diarrhea occur


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Skin disordersPsoriasisa serious, chronic, relapsing, skin ailment in which the involved skin areas produce silvery scales; areas usuaaffected are the skin of the elbow, knees, back, buttocks and scalp

Treatment used are:a. Medications such as anti-metabolites or systemic corticosteroids and methotrexate which as a folic acid antagon

it also causes malabsorption of vitamin B12, fat and caroteneb. Adequate diet as part of building up and maintaining good health; a taurine-restricted diet may be beneficial

food allergies

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