Food Allergies Lecture 24 April 20, 2015 Dr. Ponnusamy.

Food Allergies

Lecture 24April 20, 2015Dr. Ponnusamy

Department of Food Science

Lecture 24: April 20, 2015

Prevalence of food allergy• Experts agree that allergies in developed

countries are becoming more common.

• In the U.S., food allergies afflict 2-2.5% adults and 6-8% children.

• 100-175 people in the U.S. die each year.

• Death generally result from anaphylactic shock, often to peanuts or tree nuts.

• More than 160 foods have been associated with allergic reactions.



What is food allergy?

• Food allergy is an inappropriate immune response to an otherwise harmless food.

• True food allergy involves several types of immunological responses.

• Food allergens are usually proteins.

• Food allergy is not a seasonal allergy.



Understanding Immunological concepts

• Human body has many defense mechanisms to fight off infectious diseases and other toxic foreign substances.

• Strong healthy adult human can fight off most of infectious diseases.

• Ability to fight off disease can be modulated by genetics, age, race and lifestyles (diets, exercise and amount of sleep etc.)



A quick look at the Basic Terms

• Allergic reactions are Antigen-Antibody reactions

• Antigen = a foreign substance

• Antibody = a protein produced in response to an antigen that is capable of binding specifically to the antigen!

• Antibodies give immunity; also called immunoglobulins



Immunity

Innate (inborn)Genetic factors

Acquired

Active(own Ab)

Passive(Ready-made-Ab)

Natural(Exposure toForeign Agents)

Artificial(immunization)

NaturalMaternal Ab

Ab = Antibodies

Artificial(Ab fromOther sources)



Antibodies (Immunoglobulins)

• Five classes of Immunoglobulins1) IgG2) IgA3) IgM4) IgE: Found mainly in body fluids and

skin --- Associated with allergy reactions!5)IgD

Lymphocytes B in the bone marrow are commonly involved in the immunological reactions that lead to food allergy.



IgG Antibodies• found in all body fluids• Smallest• most common antibody (75% to 80%) of

all the antibodies in the body• very important in fighting bacterial and

viral infections • only type of antibody to cross placenta

in a pregnant woman for protection to fetus

http://www.webmd.com/a-to-z-guides/immunoglobulins



IgA Antibodies

• Found in nose, breathing passages, digestive tract, ears, eyes and vagina

• Also found in saliva, tears and blood• Protect body surfaces that are exposed to

outside foreign substances. • About 10% to 15% of the antibodies present in

the body are IgA antibodies. • A small number of people do not make IgA

antibodies.http://www.webmd.com/a-to-z-guides/immunoglobulins



IgM Antibodies

• Largest antibody• Found in blood and lymph fluid• First type of antibody made in response

to an infection. • They also cause other immune system

cells to destroy foreign substances. • IgM antibodies are about 5% to 10% of

all the antibodies in the body




IgE Antibodies

• Found in the lungs, skin, and mucous membranes

• Cause the body to react against foreign substances such as pollen, fungus spores, and animal dander

• Involved in allergic reactions to milk, some medicines, and some poisons

• IgE antibody levels are often high in people with allergies




IgD Antibodies

• Found in small amounts in the tissues that line the stomach or chest.

• Their mechanism of action is unclear.




What happens in a food allergy situation?

1. Food allergy is an abnormal response to a food triggered by the body’s immune system.




2. The immune responses to a food allergen produces an adverse reaction.



3. The body produces a specific type of antibody called immunoglobulin E (IgE).




• The binding of IgE to specific molecules present in a food triggers the immune response.

• The response may be mild or in rare cases it can be associated with the severe and life threatening reaction called anaphylaxis.



When does food allergy occur?

• A food allergy occurs when the immune system responds to a harmless food as if it were a threat.



• The first time a person with food allergy is exposed to the food, no symptoms occur; but the first exposure primes the body to respond the next time.

• When the person eats the food again, an allergic response can occur.



When a harmless food is perceived as a threat by the body…………………..

• In an attempt to "protect" the body, the immune system produces IgE antibodies to that food.

http://kidshealth.org/teen/food_fitness/nutrition/food_allergies.html



• IgE antibodies then trigger mast cells(which are allergy cells in the body) to release chemicals into the bloodstream.

• One of these chemicals is histamine



• Once the body has made antibodies against a certain food, those antibodies instantly recognize that food.

• Each time the person eats the food, the body releases histamine into the bloodstream again, creating allergy symptoms.

http://kidshealth.org/teen/food_fitness/nutrition/food_allergies.html



• In severe food allergies, reactions can occur even if the person touches or breathes in particles of the food.



About Histamine- 1

• Formed by decarboxylation of the amino acid histidine.

• Stored preformed in mast cells and basophils.



About Histamine- 2

• Mast cells are found in blood and lymph vessels around nerves;

• more abundant in the skin, upper and lower respiratory tract, gastrointestinal tract and reproductive mucosa.

• Histamine release– Induced by very many substances,

including IgE



Few effects of Histamine

• smooth muscle contraction of airways; airflow to lungs restricted

• increased vascular permeability: blood and immune cells cause swelling

• Pruritus- itching• gastric acid secretion• increased airway mucus secretion• esophageal contraction



Types of food allergies: Immediate & Delayed

• 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).



Types of food allergies: Immediate & Delayed

•Delayed hypersensitivity reactions (>8hours after ingestion): cellular immunity involving T-lymphocytes and macrophages



• Food allergy is a hypersensitivity reaction to normally harmless substances and involves humoral immune responses, mediated by immunoglobulin (IgE) synthesized by B lymphocytes, and cellular immune responses mediated by T lymphocytes.



• An IgE-mediated mechanism leads to clinical symptoms occurring immediately after food ingestion, e. g., "the oral allergy syndrome".

• For delayed reactions involving the gastrointestinal tract or the skin, the underlying immune mechanisms are less clear.

T lymphocytes and food allergy. Bohle B. Mol Nutr Food Res. 2004 Nov;48(6):424-33. Taken from : http://www.ncbi.nlm.nih.gov/pubmed/15508177



Stages of food allergy or hypersensitivity

• A. Sensitization: initial meeting of an allergen and the immune system that results in IgE production!

• B. Activation of mast cells – IgE– Non-IgE substances (eg. Drugs)



Most common sites for allergic reactions



Symptoms-Food Allergy*

• Nausea• Diarrhea• Abdominal cramps• Pruritic rashes• Angioedema• Asthma/rhinitis • Vomiting• Hives• Laryngeal edema• Anaphylaxis

* Exercise exacerbates symptoms



Anaphylaxis

Potential fatal reaction to a food allergen causing reduced oxygen

supply to the heart and other body tissues.

Symptoms include: difficult breathing, low blood pressure, pale skin, a weak

rapid pulse, loss of consciousness, death.



Most common allergenic foods – The Big 8

• Milk• Eggs• Peanuts• Tree nuts• Wheat • Soy• Fish• Shellfish

http://farrp.unl.edu/informallbig8



Children and Food Allergy

• High prevalence in the first few years of life

• Immature immune system and immature digestive system

• Cow’s milk and soy, most common allergens

• Breast feeding is recommended• Delay introduction of common

allergenic foods• Sensitivity to most of the allergenic foods is

usually lost by young children as they grow up



Cross-Reaction: the reaction of one antigen with antibodies developed against another antigen.

• Occurrence of allergic reactions to foods that are chemically or otherwise related to foods known to cause allergy in an individual



• If someone has a life-threatening reaction to a certain food, the doctor will counsel that patient to avoid related foods, which also might induce the same reaction.



• For example, if a person has a history of a severe allergy to shrimp, he or she can also possibly be allergic to crab, lobster, and crayfish.



Cross-Reaction



Hidden food ingredients in ready made food products

• Milk and milk product derivatives• Egg and egg derivatives• Peanuts, tree nuts and derivatives• Fish derivatives (surimi, fish sauce,

fish paste etc)• Soy and its derivatives



Milk allergies• A milk allergy is a reaction to milk

protein, casein. • Some people cannot drink cow's milk

but are fine with sheep's or goat's milk.

• Common symptoms are severe stomach pain, diarrhea, skin hives, or difficulty breathing.



Egg Allergies• In most cases, egg allergies are mild

but are caused by even tiny amounts of egg.

• Sometimes, it's the egg white (albumin) that's the problem

• For other people, it's the egg yolk. • In rare cases, an egg allergy can

trigger anaphylaxis.



Eggswww.healthcentral.com

Eggs – Many children develop an allergy to eggs, but often outgrow it. If you are allergic to eggs, be sure to check labels of food products for the following ingredients: "egg," "egg white," "dried egg" or "albumin."



Peanut allergies• One of the most common food allergies• Leading cause of deadly food allergy

reactions. • Shaking hands with someone who has

handled peanuts, or even smelling peanuts, can produce an allergic reaction in some people.

• For some people, the reaction is so severe that it causes fatal anaphylaxis.



Peanutswww.healthcentral.com

Peanuts can be found in many foods and candies, especially chocolate candy. Check all labels carefully. Once considered a lifelong allergy, recent studies indicate that up to 20% of children diagnosed with peanut allergy outgrow it. However, for people who do not out grow the allergy, their sensitivity and the severity of their reactions tends to worsen over time. Peanuts can cause severe allergic reactions. If prescribed, carry epinephrine at all times.



Tree Nut allergies• Likely to be coupled with peanut allergy• What are included in tree nuts?

– cashews, almonds, pecans, walnuts, hazelnuts, pine nuts, Brazil nuts, and macadamia nuts.

– Coconut, chestnut, ginkgo nuts, and lychee nuts are also considered tree nuts.

• Even added in nonfood products like lotions and shampoos.



Treenutswww.healthcentral.com

These also include peanuts that have been de-flavored and re-flavored with a nut, such as pecan or walnut.

For example, mandelonas are peanuts soaked in almond flavoring. Tree nuts have been used in many foods, including barbecue sauce, cereals, crackers, and ice cream.



Wheat allergy

• Allergic reactions to wheat may be caused by ingestion of wheat-containing foods or by inhalation of flour containing wheat

• Ale, beer, bourbon, and whiskey contain wheat -- and so does wine!



Wheatwww.healthcentral.com

Wheat contains several types of protein that can activate the immune system in people who have allergic action against wheat. If you have wheat allergy, check labels to be sure that even small amounts of wheat are not present in the list of ingredients. In the ingredients, look for : "wheat," "flour," "wheat germ," "wheat starch," "bran," "modified food starch," "graham flour," "farina," “spelt” and "semolina."



Wheat allergy

• 4 major proteins in wheat-albumin, globulin, gliadin and glutenin.

• The majority of IgE-mediated reactions to wheat involve the albumin and globulin fractions.



• Allergy to wheat may occur in any individual, unlike Celiac disease, which is hereditary.

• Gluten intolerance is associated with the disease called "gluten-sensitive enteropathy" or "celiac disease."



Wheat allergy

• Another manifestation of allergic reaction to wheat is really intolerance to gluten -- the protein found in wheat, rye, barley, and oats.

http://www.landfood.ubc.ca/courses/fnh/301/protein/protq4.htm



Celiac Disease

• A digestive disorder that occurs in reaction to gluten

• Gluten:– elastic, rubbery protein in wheat, rye,

barley and oats.– binds the dough in foods such as bread.– contributes to spongy consistency.

– Rice and maize (corn) do not contain gluten.



Celiac Disease

• The body's immune system reacts to the gluten and causes damage to the intestine.

• Celiac disease, also known as celiac sprue or gluten-sensitive enteropathy, is fairly common.

• One in 133 Americans has the disorder and needs to follow a gluten-free diet.



Celiac disease

• Often misdiagnosed as irritable bowel syndrome, Crohn's Disease or gastric ulcers. Digestive symptoms may include:

• Abdominal bloating and pain• Diarrhea• Vomiting• Constipation• Pale, foul-smelling stool



Celiac disease damages the Intestine

• In people with celiac disease, the body's immune system is triggered by gluten in food.

• Antibodies attack the intestinal lining, damage the villi in the small intestine.

• Damaged villi can't effectively absorb nutrients through the intestinal wall. As a result, fats, proteins, vitamins, and minerals get passed through the stool.



Changes in Villi in Celiac disease



Celiac Disease

• Failure to absorb nutrients may lead to other problems, including weight loss and malnutrition. Signs and symptoms related to weight loss or malnutrition can include:

• Anemia• Fatigue• Osteoporosis• Infertility or miscarriage• Mouth ulcers• Tingling, numbness in the hands and feet



Celiac or Wheat Allergy?

• Celiac disease and wheat allergy both involve the immune system but the reaction within the body is different

• Celiac disease is the result of IgA and IgG antibody responses to gluten

• Wheat allergy is mediated by IgE antibodies

• Celiac disease is an autoimmune disease that causes damage to the lining of the intestine. It is a lifelong disorder



Celiac or Lactose Intolerance?

• Celiac disease damages the inner lining of the small intestine, and that may lead to difficulty digesting lactose, a sugar found in milk and milk products.

• Following a gluten-free diet allows the intestine to recover, and people with celiac disease may discover that they are able to digest lactose once again.



Soy allergies

• Widely used in processed foods; very difficult to avoid.

• Ingredients/ terms like "hydrolyzed protein," "lecithin," "texturizer," "emulsifier," "protein filler," or "extender” are soy-based.



Fish allergies• Relatively easiest allergy to avoid!!!• Linked with the oral allergy syndrome

(in which the mouth itches or tingles after eating an allergen) in people with occupational contact with fish.

• The greatest risk from fish allergies is anaphylaxis: life-threatening breathing, cardiac, and gastrointestinal symptoms



Fishwww.healthcentral.com

Some people with fish allergies have reactions to more common edible “scaly” and “bony” fish, such as cod, haddock, herring, sprat, halibut, mackerel, trout and salmon. If you have any type of seafood allergy, it can be life-threatening, so you need to be aware of anything that is made with fish.



Shell fish allergies

• More likely to develop in adulthood than childhood; tend to be severe and lifelong



Shellfish allergies

• Symptoms usually appear within minutes to two hours of eating shellfish.– Skin reactions such as hives or eczema.– Allergic conjunctivitis: Itchy, red, watery eyes.– GI reactions such as nausea, abdominal pain,

vomiting, or diarrhea.– Airways symptoms such

as wheezing or coughing or runny nose.– Angioedema: Swelling of lips, tongue, or face– Anaphylaxis.



Shell fishwww.healthcentral.com

These are divided into two basic categories: “Mollusks,” include Abalone, oysters, mussels, and squid (Calamari); and “Crustaceans,” include lobsters, crayfish, prawns, crabs and shrimp.

Fish sauces



Eating out is a nightmare?

• 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.

• For traditional food restaurants, cross-contamination of allergens to other foods can also be a problem.



Solutions…

• People who have food allergy need a total avoidance of the offending foods.

• Read food ingredient list.• Eliminate cross-contamination

during cooking and preparation!!!!



Common prescribed medications

• epinephrine (relaxes smooth muscle, constricts blood vessels, and stimulates the heart; used for severe systemic reactions-anaphylaxis);

• antihistamines (block the binding of histamine to histamine receptors on target cells);

• sodium cromolyn (prevents mast cells from releasing histamines).



A strong desire to avoid a particular food

Food Aversion

Adverse reaction to food that does not involve the immune system

Food Intolerance

http://www.medicinenet.com/common_food_allergy_triggers_pictures_slideshow/article.htm



Food Intolerance

• Direct effect of food• Enzyme deficiency (e.g., lactase,

sucrase etc)• Symptoms of food intolerance: bloating,

cramping, gas and diarrhea• Main cause of food intolerance:

carbohydrates (lactose, fructose, sorbitol)



Food Intolerance

• Different from food allergy; does not involve an immunologic reaction.

• Common food intolerance: lactose intolerance.• Lactase enzyme necessary to digest lactose

(milk sugar) is lacking. • Symptoms: gas, bloating, and abdominal pain• Remedy: lactase tablets are available without

a prescription • The strategy of dealing with a food allergy is

different than dealing with food intolerance.



Allergy VS Intolerance

• True Allergy-Total avoidance necessary!

• Intolerance- Small amount may be tolerated



Other causes of allergy-like food problems

• Microbial products- e.g. histamine – Some food products have high levels of histamine (eg fermented foods)

• Pharmacological reaction-tyramine, phenylethylamine, caffiene – dose dependent

• Idiosyncratic reactions – (adverse reactions of drugs etc – dose dependent)

• Psychological disorders



Diagnosis•Determine if the symptoms are mediated by the immune system•Complete physical•Detailed case history•Food diary•Elimination Diet- by eliminating one or more potentially allergenic foods to see if reaction subsides•Positive identification of the allergen



Prick skin Test (PST) Or Scratch Test

• Drop of the substance under test on the forearm• Allow a tiny amount to enter the skin (doctor

pricks it with a needle)• After 15min, verify presence of “bump” • If the skin reddens and, more importantly, if it

swells, then the test is read as positive and allergy to that substance is considered probable.

http://www.webmd.com/allergies/ss/slideshow-food-allergy-triggers



Radioallergosorbent Test (RAST)

• Requires blood samples

• Laboratory test are performed to look if the patients has IgE against specific types of food

• If certain types of antibodies are seen in increased levels, the specific allergen could be identified.



Resources for food allergies

• Food Allergy and Anaphylaxis network (FAAN)

• American Academy of Allergy, Asthma and Immunology

• American Dietetic Association• Asthma and Allergy Foundation



Additional Info• http://www.huffingtonpost.com/2013/04/10/best-worst-food-

allergies_n_3017544.html#slide=more289760

• VIDEOS:• Food allergy testing:• https://www.youtube.com/watch?v=t144IauIoeY• Health check: https://www.youtube.com/watch?v=z6i3-

gXJQLk&list=PLr2Ihpk7tfpT0Jo_sfc6BfLGHSnD5QWu9&index=4

• Boy allergic to almost all foods: https://www.youtube.com/watch?v=BQKBh5tB1Xs• Maryland restaurant caters to food allergies:https://www.youtube.com/watch?

v=r3hxOyPXmAo&index=5&list=PLr2Ihpk7tfpT0Jo_sfc6BfLGHSnD5QWu9



Additional Info• The immune system normally protects the body from harmful

items such as bacteria or viruses. In the case of allergies, the immune system has a hypersensitivity or an allergic reaction. During an exposure to an allergen, B cells are alerted and turned into plasma cells which produce IgE (immunoglobulin E) antibodies to fight the “invader.” These antibodies travel through the body until they come into contact with the immune cells called mast cells.

• Mast cells are present in the skin, respiratory system and the gut and are important to keep us healthy by fighting off viruses, etc. The antibodies attach themselves to the mast cells via a receptor on the surface and remain attached. That way the next time the immune system meets up with the same “invader”, the system is primed to react again.

http://allergicliving.com/2013/09/15/disordered-mast-cells-and-the-clues-to-food-allergy/



Food Allergy Webinar

A presentation of food allergy basics by Eleanor Garrow, Vice President of Education and Outreach for FAAN (Food Allergy & Anaphylaxis Network).

• http://www.youtube.com/watch?v=TOEobQYgKNI

Food Allergies Lecture 24 April 20, 2015 Dr. Ponnusamy.

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