Food Allergies

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Food Allergies

• Lecture 24
• April 22, 2013
• Dr. Ponnusamy

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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.

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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.

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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.)

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Basic Terminology

• 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!

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Specific Immunity
Immunity
Ab Antibodies
Acquired
Innate (inborn) Genetic factors
Passive (Ready-made-Ab)
Active (own Ab)
Natural Maternal Ab
Artificial (Ab from Other sources)
Natural (Exposure to Foreign Agents)
Artificial (immunization)
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Antibodies (Immunoglobulins)

• Produces by B-lymphocytes (bone marrow)
• Five classes of Immunoglobulins
• 1) IgG
• 2) IgA
• 3) IgM
• 4) IgE Found mainly in body fluids and skin ---
  Associated with allergy reactions!
• 5) IgD

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IgG Antibodies

• Found in all body fluids
• Smallest most common antibody
• (75 to 80) of all the antibodies in the body.

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IgG Antibodies

• Vital in fighting bacterial and viral infections.
• The only type of antibody that crosses
  the placenta in a pregnant woman to help protect
  her fetus.

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IgA Antibodies

• Found in nose, breathing passages, digestive
  tract, ears, eyes, and vagina.
• Also in saliva, tears and blood
• IgA antibodies protect body surfaces that are
  exposed to outside foreign substances.

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IgA Antibodies

• About 10 to 15 of the antibodies present in the
  body are IgA antibodies.
• A small number of people do not make IgA
  antibodies

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IgM Antibodies

• The largest antibody.
• Found in blood and lymph fluid
• The first type of antibody made in response to an
  infection.

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IgM Antibodies

• Cause other immune system cells to destroy
  foreign substances.
• IgM antibodies are about 5 to 10 of all the
  antibodies in the body.

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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.

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IgE Antibodies

• Occur in allergic reactions to foods, some
  medicines, and some poisons.
• IgE antibody levels are often high in people
  with allergies.

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IgD Antibodies

• Found in small amounts in the tissues that line
  the stomach or chest.
• Their mechanism of action is unclear.

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What happens in a food allergy situation?

• Food allergy is an abnormal response to a food
  triggered by the bodys immune system.
• The immune responses to a food allergen produces
  an adverse reaction.
• The body produces a specific type of antibody
  called immunoglobulin E (IgE).

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• 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.

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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.

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Histamine

• Formed by decarboxylation of the amino acid
  histidine.
• Stored preformed in mast cells and basophils.

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More about Histamine

• 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

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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

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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).

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Types of food allergies Immediate Delayed

• Delayed hypersensitivity reactions (gt8hours after
  ingestion) cellular immunity involving
  T-lymphocytes and macrophages

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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)

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Most common sites for allergic reactions
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Symptoms-Food Allergy

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

Exercise exacerbates symptoms
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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.

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Most common allergenic foods The Big 8

• EGGS
• MILK
• PEANUTS
• TREE NUTS
• SOY
• WHEAT
• FISH
• SHELLFISH

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Children and Food Allergy

• High prevalence in the first few years of life
• Immature immune system and immature digestive
  system
• Cows 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

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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

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• 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.

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• 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.

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Cross-Reaction
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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

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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.

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Egg Allergies

• In most cases, egg allergies are mild but are
  caused by even tiny amounts of egg.
• Sometimes, it's the egg white (albumen) that's
  the problem
• For other people, it's the egg yolk.
• In rare cases, an egg allergy can trigger
  anaphylaxis.

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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." 
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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.

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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.
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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.

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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.
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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.
•  

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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."
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Wheat allergy

• 4 major proteins in wheat-albumin, globulin,
  gliadin and glutenin (gluten)-vary in proportion
  according to the type of wheat.
• 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.

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Wheat allergy

• Another manifestation of allergic reaction to
  wheat is really intolerance to gluten -- the
  protein found in wheat, rye, barley, and oats.
• Gluten intolerance is associated with the disease
  called "gluten-sensitive enteropathy" or "celiac
  disease."

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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 do not contain gluten.

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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.

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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

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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.

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Changes in Villi in Celiac disease
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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

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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.

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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.

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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.

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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

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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.
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Shell fish allergies

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

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Shell fishwww.healthcentral.com
These are divided into two basic categories
Molluscks, include Abalone, oysters, mussels,
and squid (Calamari) and Crustaceans, include
lobsters, crayfish, prawns, crabs and
shrimp. Fish sauces
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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.

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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!!!!

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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).

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Additional Info

• http//www.huffingtonpost.com/2013/04/10/best-wors
  t-food-allergies_n_3017544.htmlslidemore289760

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Food Aversion

• A strong desire to avoid a particular food

Food Intolerance
Adverse reaction to food that does not involve
the immune system
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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)

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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.

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Allergy VS Intolerance

• True Allergy-Total avoidance necessary!
• Intolerance- Small amount may be tolerated

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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

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Diagnosis

• Determine if the symptoms are mediated by the
  immune system
• Complete physical
• Detailed case history
• Food diary
• Positive identification of the allergen

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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.

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Radioallergosorbent Test (RAST)

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

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Resources for food allergies

• Food Allergy and Anaphylaxis network (FAAN)
• American Academy of Allergy, Asthma and
  Immunology
• American Dietetic Association
• Asthma and Allergy Foundation

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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?vTOEobQYgKNI