Food Allergies…

Food Allergies The food of one may be poison for another. Lucretius De Rerum Natura

What is food allergy? l an adverse reaction to a food that is mediated by an immunologic mechanism; occurs consistently after consumption of that food and causes functional changes in target organs; food hypersensitivity l True food allergy involves several types of immunological responses. l Food allergens are usually proteins. Some foods may contain haptens or haptens carrier. (A hepten- a small molecule that has the ability to combine with an Ab or a cell-surface receptor.) Some foods may contain haptens or haptens carrier. (A hepten- a small molecule that has the ability to combine with an Ab or a cell-surface receptor.)

l Food and symptom diary: a record of food and drink consumed and symptoms experienced l Food Hypersensitivity: food allergy l Food Intolerance: an adverse reaction to a food caused by toxic, pharmacologic, metabolic, or idiosyncratic reactions to the food or chemical substances in the food l Idiosyncrasy: a food reaction that resembles allergy but may actually be caused by individual intolerance

l Rotation Diet: an eating plan in which several foods known to cause allergic reactions or which are not tolerated, are eaten on separate days and then only every fourth or fifth day for each food l Sensitization: exposure to an antigen or allergen that results in the development of hypersensitivity

Definitions l Elimination Diet: an eating plan in which individual foods suspected of causing intolerance or allergic reactions are omitted for a period of time in order to determine if the individual’s condition improves

Food Sensitivities (Individualistic Adverse Reactions to Foods) Food Allergy Food Intolerance

Food Allergy (Food Hypersensitivity) IgE-Mediated Exercise-induced Cell-Mediated Celiac Disease

Types of food allergies l Immediate hypersensitivity with IgE which occurs within minutes to a few hours after ingestion of offending foods. –Systemic: Itching, urticaria (hives), Vomiting, Abdominal cramps, diarrhea and respiratory distress, and in severe cases anaphylactic shock –Localized: hives and eczema or atopy (an umbrella term covering clinical presentations of food allergy etc) l Delayed hypersensitivity reactions (>8hours after ingestion): cellular immunity involving T- lymphocytes and macrophages

Mechanisms of Mediator Release

How prevalence is food allergy? l Experts agree that allergies in developed countries are becoming more common. l In the U.S., food allergies afflict 2-2.5% adults and 6-8% children. l people in the U.S. die each year. l Death generally result from anaphylactic shock, often to peanuts or tree nuts. l More than 160 foods have been associated with allergic reactions. C&EN/January 7, 2002 page 21.

Common Food Allergens l many foods implicated in food allergy l relatively few foods have been documented to cause adverse reactions l antigens in food are often large proteins (mw 10,000 to 70,000 daltons) l cross-reactivity between antigens may occur l allergy to one food or pollen does not mean allergy to all related foods l antigens of some foods are removed by processing

90% Peanut Tree nuts Milk Egg Soy Fish Shellfish Wheat 10% Hundreds of others Food Allergies Prevalence Food Allergies Prevalence

Common Allergens by Age Group l Infants/Children –egg –fish –milk –peanuts –soy –wheat l Adults –fish –nuts –peanuts –shellfish –soy

It is not easy…living with food allergies! What would you choose to eat, if you are allergic to milk or dairy products?

Hidden food ingredients in ready made food products! l Milk and milk product derivatives l Egg and egg derivatives l Peanuts, tree nuts and derivatives l Fish derivatives (surimi, fish sauce, fish paste etc) l Soy and its derivatives

What about food Additives? l Sulfur-based preservatives F Sulfites l Aspartame (a sweetener)- PKU l Monosodium glutamate l FD&C Yelow #5 (Tartrazine)

Cross-Reactions: Food and non-food allergens l Ragweed- Watermelon, cantaloupe, honeydew, bananas l Mugwort- celery l Birch pollen-carrots, apples, hazelnuts, potatoes l Banana – latex l * If allergic to one shellfish or legumes, likely allergic to all!

To make the matter worse! l Eating out is a nightmare? l African, Chinese, Indonesian, Mexican, Thai, and Vietnamese dishes often contain peanuts. It is recommended that peanut-allergic individuals avoid these types of foods and restaurants. l For traditional food restaurants, cross- contamination of allergens to other foods can also a problem.

What Are the Causative Agents of Food Allergies? l Naturally-occurring proteins l Heat-resistant l Resistant to proteolysis l Resistant to extremes in pH l Usually major proteins of the food l Foods can have 1 or many allergens in them

Allergens l Virtually all allergens are proteins BUT not all proteins are food allergens l Foods contain tens of thousands of proteins - very few are allergens l Many allergens stable to digestion and processing l Major allergens tend to be abundant proteins

How Much is Too Much? Milligram amounts! (ppm concentrations)

Symptoms of Food Allergy l Gastrointestinal –abdominal pain –nausea l vomiting –diarrhea –GI bleeding –protein-losing enteropathy –oral & pharyngeal pruritus l Cutaneous –urticaria –eczema –angioedema –erythema –itching l Systemic –anaphylaxis

l Respiratory –rhinitis –asthma –cough –milk-induced syndrome with respiratory disease (Heiner’s syndrome) l Controversial or unproven –behavioral conditions –tension-fatigue syndrome –attention deficit hyperactivity disorder –otitis media –psychiatric disorders –neurologic disorders –musculoskeletal disorders –migraine headache

Primary and secondary responses to an antigen Primary response: first response when host’s B-cell recognize the antigen Secondary response: upon second exposure to the antigen, the Memory cells will divide, thus make more of the total antibody

Risk Factors for Development of Food Allergy l Heredity l Exposure to the food (antigen) l Gastrointestinal permeability l Environmental factors

Factors Influencing Symptoms l Amount of antigen (allergen) ingested l Amount of antigen (allergen) absorbed l Types of reactions that occur l Sensitivity of the target organ

Severity of Allergic Reactions to Foods l In rare cases, life-threatening reactions can occur l Degree of sensitivity to the offending food varies from individual to individual l Severity will be related, to some extent, to the dose of exposure l Records are not kept on the number of deaths from food allergies but probably have per year in U.S.

Food-Induced Anaphylaxis is Not a Rare Occurrence l Researchers estimate 29,000 emergency room visits and deaths per year due to food-induced anaphylaxis(U.S.) –Bock et al. J. Allergy Clin. Immunol. 2001;107: l Danish study: 5% fatality rate –Sorensen et al. Allergy 1989;44:28-29.

Food Intolerances l Food additives –preservatives F MSG –flavor enhancers –coloring agents l sulfites l carbohydrate intolerance –lactase deficiency

Diagnosis l No simple test to diagnose food allergy l Diagnosis requires: –identification of the suspected food –proof that the food causes an adverse response –verification of immunologic involvement l Nonallergic mechanisms must be ruled out.

History l First tool in diagnosis l Information needed: –description of symptoms –time from ingestion of food to onset of symptoms –description of most recent reactions –list of suspected foods –estimate of quantity of food required to produce a reaction –early feeding history –family history of allergy

Physical Examination l Plot on growth chart. Evaluate in relationship to earlier measurements. –Weight –Height –Head circumference for infant l Assess for clinical signs of malnutrition –evaluate fat and muscle stores l Evaluate for evidence of chronic conditions –eczema, rhinitis, and asthma

Food and Symptom Diary l Kept for 1-2 weeks l Record: –type of food –time and amount eaten –time of appearance of symptoms –medications taken l Reasons –helps document symptoms –may suggest relationships to diet not apparent from recall –also serves as baseline for future intervention

Biochemical Testing l CBC with differential l Tests of stool for: –reducing substances –ova –parasites –occult blood l Sweat chloride test

Immunologic Testing l Reliable tests: –Skin-prick test –RAST test –Elisa l Unreliable Tests: –cytotoxic testing –sublingual testing –provocative and neutralization testing –kinesiologic testing

Food Elimination l Suspected foods omitted from the diet for 2 weeks or until symptoms clear l If symptoms do not clear and food allergy is still suspected, more restrictive diets can be implemented l If symptoms still persist, causes other than the foods eliminated should be investigated l Food diary kept during elimination phase

Food Challenge l Made after symptoms have cleared. l Foods are reintroduced (challenged) one at a time while the person is carefully observed for the recurrence of symptoms. l May precipitate anaphylactic reactions. l Double-blind, placebo-controlled food challenge (DBPCFC). –When symptoms are subjective. –When multiple food allergies suggested. –When psychosocial components suspected.

Treatment for True Food Allergies Specific Avoidance Diets

Food Allergies Avoidance of the offending food is the most effective mode of treatment for patients with food allergies DRUG(S) OF CHOICE Symptomatic treatment, e.g., antihistamine Symptomatic treatment, e.g., antihistamine The use of cromolyn has been suggested, but is not practical for use in most patients with food allergy The use of cromolyn has been suggested, but is not practical for use in most patients with food allergy Recent studies have suggested the use of ketotifen, which is a mast cell stabilizer. This drug is not available in the United States. Recent studies have suggested the use of ketotifen, which is a mast cell stabilizer. This drug is not available in the United States.

l Eliminate offending food from the diet. –Individual sensitivity determines degree to which foods must be omitted. –Nutritional counseling essential. –Restricted foods may be “hidden” in the diet. –Alternative nutrient sources must be provided. l Rotation diet. l Not viable treatments for food allergy: –Desensitization treatments. –Medications. l Prophylactic use of sodium cromolyn.

Problems with Specific Avoidance Diets l Degree of selectivity l Knowledge of food composition l Exquisite sensitivity l Adequate nutrition l Restaurant meals l Confusing labeling terms

Prevention of Food Allergy in Children at High Risk for Allergy l Exclusive breastfeeding for first 6 months l Withhold highly allergenic foods such as milk, egg, peanuts, and fish for the first 2 to 3 years of life

Other causes of allergy-like food problems l Microbial products- e.g. histamine – Some food products have high levels of histamine (eg fermented foods) l Pharmacological reaction-tyramine, phenylethylamine, cafiene – dose dependent l Idiosyncratic reactions – (adverse reactions of drugs etc – dose dependent) l Psychological disorders

Resources for food allergies l Food Allergy and Anaphylaxis network (FAAN) l Other resources l See handouts