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Judith E. Brown
www.cengage.com/nutrition/brown
Food Allergies and Intolerances
Unit 17
Prof. Albia Dugger • Miami-Dade College
Food Allergy
• Food allergies are a major health concern in
the US and other Westernized countries
• Food allergy (food hypersensitivity)
• Adverse reaction to a normally harmless
substance in food that involves the body’s
immune response
Adverse Reactions to Foods
• Food intolerance
• Adverse reaction to a normally harmless
substance in food that does not involve the
immune system
• Immune system
• Body tissues that provide protection against
bacteria, viruses, and other harmful substances
Adverse Reactions to Foods
• Foods that often cause adverse reactions:
Allergy and the Immune System
• In people with allergies, body cells identify
some components of food as harmful and
trigger the body’s immune system
• Food allergen
• Substance in food (usually protein) that the body
identifies as harmful and that elicits an allergic
reaction from the immune system
Allergy and the Immune System
• In response to an allergen, the immune
system forms antibodies
• Antibodies
• Proteins the body makes to fight harmful invaders
such as viruses, bacteria, or (in the case of food
allergies) allergens
Allergy and the Immune System
• Antibodies are formed on first exposure to an
allergen – when the allergen reappears, an
allergic reaction occurs
• Histamine
• Substance released in allergic reactions
• Causes blood vessel dilation, itching, hives, drop
in blood pressure, release of stomach acids
• Counteracted by antihistamines
Development of Allergic Reaction
Food Allergy Symptoms
Anaphylactic Shock
• In highly sensitive
people, exposure to
trace amounts of an
allergen can cause
anaphylactic shock – a
massive immune
reaction that can result
in death
Key Terms
• Anaphylactic shock
• Reduced oxygen supply to the heart and other
tissues due to the body’s reaction to an allergen
in food or other “foreign” substance
• Symptoms may include abdominal cramps,
vomiting, chest tightness, paleness, weak and
rapid pulse, difficulty breathing
• Can result in death
• Treated with epinephrine injection
Foods Most Likely to Cause Allergy
• Food ingredient labels
are required to state
whether a food contains
one or more of the “big
eight” food allergens
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Nuts
Eggs
Wheat
Milk
Peanuts
Soy
Shellfish
Fish
Foods Most Likely to Cause Allergy
Wheat Allergy (Celiac Disease)
• Celiac disease (celiac sprue or gluten
sensitive enteropathy)
• An autoimmune disease characterized by
inflammation of the small-intestine lining resulting
from a genetic gluten intolerance
• Causes diarrhea, fatty stools, weight loss, vitamin
and mineral deficiencies
• Treated with gluten-free diet
Gluten in Foods
How Common Are Food Allergies?
• 5% of infants and children develop a food
allergy, often to cow’s milk or egg white
• For children at risk:
• No cow’s milk before age 1
• No eggs before age 2
• No peanuts, nuts, fish, shellfish before age 3
How Common Are Food Allergies?
• 2-3% of adults have food allergies, and the
number is increasing
• About 1/3 of Americans believe they have
food allergies – but usually, allergy is not
confirmed by testing
Diagnosing Food Allergy
• Double-blind, placebo-controlled food
challenge
• Test used to determine the presence of a food
allergy or other adverse reaction to a food
• Neither patient nor care provider knows whether
the suspected food or a placebo is being tested
• Undertaken under medical supervision
Other Tests for Food Allergy
• Immunoglobin-E test
• IgE protein produced in
response to an allergen
• Doesn’t identify allergen
• Skin prick tests
• For absence of food
allergy only – positive
results don’t prove an
allergy exists
• Positive skin-prick test
Bogus Tests
• Companies that offer food allergy tests
through the mail do not use reliable
techniques and are a waste of money
• Other unreliable tests:
• Hair analysis, cytotoxic blood tests, iridology,
sublingual food injection provocation
Treating Food Allergies
• Allergy shots for food allergens are not yet
available
• After an allergy is confirmed, the only
treatment is to eliminate the food from the diet
Food Intolerances
• Food intolerance does
not involve the immune
system
• Produces reactions
similar to food allergy,
but by different
mechanisms
Lactose Maldigestion
• Lactose maldigestion
• Characterized by reduced digestion of lactose
due to low availability of the enzyme lactase
• Occurs in 25% of US adults; incidence varies by
population group
• Results in lactose intolerance
Lactose Intolerance
• Lactose intolerance
• GI symptoms resulting from consumption of more
lactose than can be digested with available
lactase
• Flatulence, bloating, abdominal pain, diarrhea,
“rumbling in the bowel” due to breakdown of
undigested lactose by intestinal bacteria
• Restricts intake of lactose-containing products
Sulfite Sensitivity
• Sulfite is a food additive
(preservative) used in
many foods and
medications
• Small amounts can
cause anaphylactic
shock in sensitive
people
Red Wine, Aged Cheese,
and Migraines
• Histamine in some foods may cause migraine
headaches in sensitive people
• Red wine, beer, sardines, anchovies, cured
sausages, pickled cabbage, spinach, catsup
• Tyramine may cause similar symptoms
• Aged cheese, soy sauce, and other fermented
products
“Chinese Restaurant Syndrome”
• MSG (monosodium glutamate) is used as a
flavor enhancer in soups, stews, and many
Chinese food items
• “Chinese restaurant syndrome”
• Sensitivity causes dizziness, sweating, flushing,
rapid heartbeat, and ringing in the ears
Precautions
• People with food allergies or intolerances
must be very careful about what they eat
• They should have a plan of action ready in
case a serious reaction develops
Take Action to Prevent Anaphylaxis
• For those at risk of anaphylactic shock:
• Learn how to avoid foods that trigger reactions
• Ask your doctor what to do if symptoms appear
• Fill and carry prescriptions for any needed
medications (EpiPens, antihistamines, inhalers) –
and learn how to use them
• Wear an ID bracelet with allergy information