A food allergy is an adverse reaction to a food or food component that involves the immune system
A food allergen is the part of a food a person is allergic to
Food allergens are proteins not fat carbohydrates vitamins or minerals
2-5 in infants most common milk and eggs
2.4 in adults
3 Who Has Food Allergies
Although anyone can develop a food allergy the ability to become allergic tends to be inherited
Many people who have food allergies also have asthma or show sensitivities to inhaled allergens such as dust cat and pollen
4 What Happens WithA Food Allergy
When someone eats a food they are allergic to the food allergen stimulates the immune system to release antibodies
The antibodies cause body cells to release substances which cause allergic reactions
5 Most Common Food Allergies
Food allergies can occur to almost any food but most allergic reactions are caused by a limited number of foods
wheat peanuts most common anaphylaxis
fish tree nuts like walnuts
Additives preservatives flavoring coloring antioxidants cause Pseudo-allergenic reactions
6 Where does it start
According to a recent study the prevalence of peanut allergy--which accounts for the majority of emergency-room visits and deaths related to food allergies each year--doubled between 1997 and 2002.
The story of food allergy is a story about how the development of the immune system is tightly linked to the development of our digestive tract or as scientists and physicians usually refer to it our gut. A human being is born with an immature immune system and an immature gut and they grow up together. The immune system takes samples of gut contents and uses them to inform its understanding of the world--an understanding that helps safeguard the digestive system (and the body that houses it) against harmful microorganisms.
The window for fine-tuning a babys mucosal immune system is relatively narrow starting when the infant is colonized with vaginal and intestinal bacteria from the mothers birth canal
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!
Haptens - a small molecule that has the ability to combine with an Ab or a cell-surface receptor.
8 Our immune systems
Immune cells are woven into the fabric of the gut than being restricted to one place but there are discrete structures for immune surveillance.
Membrane cells (M-cells) recognize antigens and pass them to bone marrow cells (B-cells) Thymus cells ( T-cells) and antigen presenting cells (APC) such as macrophages and dendritic cells
Activated B cells start producing antibodies
9 Understanding Immunological concepts
Food allergies are related to specific defenses or specific immunity
Immune literary means free of burden
Actions of the immune system are triggered by antigens (foreign substances).
Most antigens are large protein molecules Some antigens are polysaccharides and few are glycoproteins (carbohydrate and protein) or nucleo-proteins.
10 Understanding Immunological concepts
Human body has two categories of defense system
Non specific defenses
Physical barriers (skin and mucous membrane)
Chemical barriers (saliva mucus gastric juices etc)
Cellular defenses (certain cells can eat invaders-phagocytes)
Inflammation (reddening swelling and temperature increase of the affected sites)
Fever (elevated body temperature)
Molecular defenses (interferons or complementary system etc.)
Specific defenses or specific immunity
Antibodies (many kinds of antibodies for many kinds of antigens)
11 Acquired-Active-Natural Specific Antibodies (Immunoglobulins)
There are five classes of Immunoglobulins
1) IgG Main class of antibodies in blood-also from mother-to-child (20)
2) IgA Small amount in blood but larger amount in tears milk saliva mucus and the lining tissues
3) IgM First Antibody secreted during the primary response
4) IgE (Reagin) Found mainly in body fluids and skin --- Associated with allergy reactions!
5) IgD Found in B-Cell membrane
12 Who makes the immunoglobulin IgE The allergen enters the body and is recognized by sIg on a B-lymphocyte. The B-lymphocyte proliferates and differentiates into plasma cells that produce and secrete IgE against the allergen. Picture credit used with permission from Dr. Gary E. Kaiser http//www.cat.cc.md.us/courses/bio 141/lecguide/index.html 13 Whats next The next time the allergen enters the body it cross-links the Fab portions of the IgE bound to the mast cell. This triggers the mast cell to degranulate that is release its histamine and other inflammatory mediators.
Picture credit used with permission from Dr. Gary E. Kaiser
When released from mast cells histamine causes vasodilation and an increase in permeability of blood vessel walls. These effects in turn cause the familiar symptoms of allergy including a runny nose and watering eyes. When released in the lungs histamine causes the airways to swell shut in an attempt to close the door on offending allergens and keep them out. Unfortunately the ultimate result of this response is the wheezing and difficulty in breathing seen in people with asthma - an occasionally deadly allergic complication which kills an estimated 4000 Americans yearly.
16 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
17 To make the matter worse!
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 a problem.
18 Food Allergy Symptoms
Allergic reactions to foods usually occur within minutes to a few hours after eating an offending food
In very sensitive people even smelling or touching the offending food may produce an allergic reaction.
Food allergies vary in their severity and how swiftly symptoms appear. The immediate life-threatening reactions experienced by some people (most often to peanuts) happen when the allergen binds to IgE-type antibodies which then trigger the release of histamine the compound responsible for acute inflammation with itching sneezing and other allergy symptoms
19 Food Allergy Symptoms
Food allergy reactions vary from person to person as well as within the same person
The same food can produce totally different symptoms in different people as well as varying symptoms within the same person
20 Symptoms-Food Allergy
Exercise exacerbates symptoms 21 Symptoms
Nose Throat and Lung Reactions -Sneezing nasal congestion runny nose chronic cough shortness of breath or other breathing difficulties asthma
Stomach and Intestinal Reactions -Nausea abdominal pain and bloating vomiting diarrhea cramping gas
Skin - Swelling of lips mouth tongue face or throat hives rashes itching skin redness
Different parts of the body experience food allergy reactions at the same time
Reactions can progress rapidly and may include itching hives sweating swelling of the throat breathing difficulties lowered blood pressure unconsciousness and even death
23 Severe Allergy Reactions
Most food allergic reactions are mild but a small number of food-allergic individuals have severe reactions that can be life-threatening
Anaphylaxis is rare but can be a possibly fatal food allergy reaction
24 Have A Plan
People who have severe allergic reactions need to plan for handling emergency situations
May carry epinephrine for self-injection and warning medical alter bracelets or necklaces in case they become unconscious
25 How to deal with food allergy!
There is no specific antibody for any specific foods available!
People who have food allergy need a total avoidance of the offending foods.
Read food ingredient list.
Eliminate cross-contamination during cooking and preparation!!!!
26 Common medications prescribed by doctors
epinephrine (relaxes smooth muscle constricts blood vessels and stimulates the heart used for severe systemic reactions)
antihistamines (block the binding of histamine to histamine receptors on target cells)
sodium cromolyn (prevents mast cells from releasing histamines).
27 Living With A Food Allergy
The only proven treatment for a food allergy is to avoid the offending food
A elimination diet must be carefully developed and be personalized to take into account the ability of an individual to tolerate an allergic food
28 Living With A Food Allergy
Using an elimination diet for 1-2 years may promote outgrowing a food allergy
Some food allergies particularly to peanuts nuts fish and shellfish can last a lifetime
No drugs are available to treat food allergies
29 Proper Diagnosis
Elimination tests and food challenges should be conducted only under medical supervision
ELISA and RAST are reliable tests for diagnosing allergies
Cytotoxic testing and symptom provocation are unreliable methods
30 RAST or ELISA
Radioallergosorbent test (RAST) or enzyme-linked immunosorbent assay (ELISA) are reliable skin-prick testing and blood testing for diagnosing allergies.
Two unreliable methods for diagnosing food allergies are cytotoxic testing and symptom provocation testing where a dose of the food extract is placed under the tongue or injected.
31 How about 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)
True Allergy-Total avoidance necessary!
Intolerance- Small amount may be tolerated
32 Food allergy and biotechnology
Although it is not easy to predict potential allergenicity of foods derived from GMO! there are some criteria to go by
Sources of transferred genetic material While the crops from staple foods are derived contain tens of thousands of different proteins relatively few are allergenic.
Synthesis of allergenic proteins also depends on the growing conditions and other stress factors.
Molecular weight of most known allergens are between 10000 and 40000.
33 Food allergy and biotechnology
The amino acid sequence of many allergens is readily available.
Labile allergens in foods that are eaten cooked or undergo other processing before consumption are of less concern.
Most allergens are resistant to gastric acidity and to digestive proteases.
New proteins expressed in non-edible portions of plants for example are not of a concern in terms of food allergy.
34 Resources for food allergies
Food Allergy and Anaphylaxis network (FAAN)
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