4. Food Allergy and Intolerance

Question 1

What is Allergy?

Answer 1

Allergy is hypersensitivity disorder of the immune system which is triggered by an allergen.

An Allergen (or antigen) is any substance that causes the allergic response (generally a protein) - there are a few common groups of allergens (about 160 foods)

Allergy involves INFLAMMATION (either generalised or systemic) in atopic individuals

Question 2

What happens in an allergic reaction?

Answer 2

IgE vs non-IgE mediated reactions

• IgE mediated = widespread mast cell degranulation
• Non IgE mediated not life threatening or life ending

Immediate (type 1 hypersensitivity) vs. delayed

Generalised vs. Localised

inhalation, consumption, absorption

Mast cell degranulation

Question 3

Whats going on?

Answer 3

The immune system is hypersensitive and reacts

• Respond in abnormal way to a particular protein
• In food allergy, small amounts of the protein crosses intact from the gut into the blood

Contact with allergen sets off a cascade of events - this determines symptoms, treatment and planning and future

Question 4

An allergic Reaction can be immediate or Delayed- whats the difference?

Answer 4

Immediate = usually IgE mediated: results in HIVES, Tissue swelling, breathing difficulties and can often cause ANAPHYLAXIS- may also cause hay fever and asthma

Delayed= non IgE mediated
- Eczema, contact dermatitis, abdominal pain, vomiting etc. Rarely causes anaphylaxis

Question 5

What is defined as a MILD allergic reaction?

Answer 5

Itching (face and neck)
Hivers and welts (rash)
Swelling lids, eyes, face

Question 6

What is defined as a MODERATE allergic reaction?

Answer 6

Mild +
Generalised Rash
Vomiting
Abdo pain
Diarrhoea

Question 7

What is defined as a SEVERE allergic reaction?

Answer 7

Moderate +

Swelling tongue + throat
Difficulty breathing
Noisy breathing
Distress anxiety
Loss of consciousness
Difficulty talking
Wheeze
Cough
Pale and Floppy

Question 8

Immediate Allergic Reactions- TYPE 1- explain the mechanism, onset, and the IgE mediated Response!

Answer 8

Type 1: Immediate hypersensitivity (anaphylactic)- IgE mediated

Mechanism: degranulation of mast cells & release of histamines and mediators

onset: Minutes to hours

Eg. urticarial, allergic rhinitus

IgE mediated response
- Cells recognise antigen as “foreign” and make antibodies, IgE against it.
-IgE binds to mast cells on high affinity receptors, sensitising the mast cells.
- Subsequent exposure to the allergen causes the sensitised mast cells to degranulate- break open - & release histamine/other substances -> inflammatory reaction (swelling and inflammation) =>
This causes a cascade of events & reactions

THE IMMUNE RESPONSE
- So it is not the first response you are worried about, its the next time they are exposed

Question 9

Explain the effect of mast cell degranulation in the

a- GIT

b- Airways

c- Blood Vessels

Answer 9

a- GIT: Increases fluid secretion, increased peristalsis, expulsion of GIT contents (vomiting and diarrhoea)
- Attempt to get rid of what it determines as a threat

b- AIRWAYS: Decreased diameter, increased mucous secretion; Congestion, blockage of airways (wheeze, cough, phlegm, stridor), Swelling of nasal passage

c- BLOOD VESSELS: increased blood flow, increased permeability; increased in tissues and extracellular spaces- causing oedema -&raquo_space; unable to maintain BP–> causes significant hypotension

Question 10

Explain Non-IgE mediated response to allergens

Answer 10

Not anaphylaxis, not life threatening

Delayed: 2-3 days

Not IgE immune response can occur

Looking more at whats considered to be intolerance but are not life threatening -> just uncomfortable

Question 11

What defines Anaphylaxis?

Answer 11

Rapidly progressive allergic reaction that is potentially life threatening and can be fatal

“A generalised allergic reaction that has signs and symptoms which indicate involvement of the respiratory/cardiovascular system or both

Anaphylaxis is a medical emergency- it requires immediate treatment, it can be fatal.

Question 12

WHAT IS the prevalence of anaphylaxis?

Answer 12

Australia has the highest prevalence rates of allergic disease.
Highest prevalence of peanut allergy in infants

Peanuts we are exposed to are ROASTED - here you get a change in the protein- maybe it is this

either way, the 0-4 year olds are the biggest risk, no communication can be given to adivse how they are fealing

1% of food reactions are life threatening

8-16% of anaphylaxis occurs in school/child care

Australia: 600% more EpiPens and Anapens than other countries- and deaths still occur

Up to 16% of anaphylaxis occurs at school or in childcare

Question 13

Name some common allergens

Answer 13

Over 95% of all food allergies come from these 7 foods:
-Eggs, Shellfish, fish, milk, peanuts, soy and wheat

• Kiwifruit and avocado over the past 5 years has been creeping up.
  Majority of kids who have one allergy will have more than 1, many will outgrow them

Question 14

Common allergens in young children

Answer 14

Cows Milk
Soy
Egg**
Peanuts**
Tree Nuts**
Wheat

Development of gut flora
If they havent been exposed to particular bacteria or if their gut flora isnt developed they wont handle the addition of food groups

If there is a family hx of peanut allergy & mother eats nuts whilst breast feeding, child more likely to develop anaphylaxis

Question 15

Common allergens in older children and adults

Answer 15

Peanuts*
Tree Nuts*
Egg*
Seeds
Shell Fish
Fish

Question 16

Milk Allergy

Answer 16

2% of babies are dairy allergic. Most out grow it within a few years

Problems:
-Many foods contain dairy products usually also allergic to goats milk
-Eliminating dairy products –> nutritional deficiencies (ca, protein) so need advice from a dieticion)
Allergy to human breast milk is virtually unknown

Question 17

Soy Allergy

Answer 17

Common in Infancy -> Grow out of it

Soy present in many processed foods

Question 18

Egg Allergy

Answer 18

2% of babies are allergic to egg, most grow out of it

Problems

• Many foods contain egg products- perfect early food
• Touching the shell of the egg can be enough!
• Usually also allergic to other eggs
• Fortubnately cooking may reduce allergenicity (denatures some of the protein)

Question 19

Seafood Allerg

Answer 19

usually a LIFE LONG problem
May be allergic to crustaceans (crab, prawns), molluscs (oysters, clams) or scale fish (tuna)

But usually less likely to be exposed early

Question 20

Wheat and other cereals (rye, corn, oat) Allergy

Answer 20

Typically in infants often outgrown in a few years (often hav grass pollen hey fever)

Difficulty: wheat flour occurs in many processed foods
Distiinguish allergic reactions (IgE) to wheat from coeliac disease (autoimmune) - if there is an immune response (IgE) we can determine how severe it is

Question 21

PEANUT ALLERGY

Answer 21

0. 5% of infants (1:200)
   - 0-4 years

Many show only mild symptoms, some develop life threatening anaphylaxis

Most severe type of reaction: lack of appropriate communication, exposure at childcare, age wheere they put everything in their mouth

• Much higher area of risk because incidental or accidental exposure is much higher in these kids
• More likely to put something in their mouth because they dont know any better -> leads to high level of anxiety from a family

It is life long

Exposure is hard to avoid

Question 22

Tree Nut Allergy

Answer 22

Rare alergy, but can be serious

Not as common as peanuts:

• Almonds
• Brazil nuts
• Cashews
• Chestnuts
• Hazelnuts
• Maccadamia nuts
• Pecans
• Pine Nuts
• Pistachios
• Wallnuts

Question 23

Food Intolerance!

Answer 23

IS NOT the same as food allergy- it is not anaphylaxis- there is no immune response

Does not involve the immune system

Cannot cause anaphylaxis

Most common form is lactose intolerance

One of the conditions that people self diagnose more than anything else!

Results in vomitting, diarrhea, and abdominal pain

Question 24

Allergy Vs. Intollerance

Answer 24

Symptoms
Time of onset
 - if its immediate type hypersensitivity it will be immediate onset
- Food intolerance will be over a few hours- days
-
Non IgE mediated response
Non Life threatening
NOT anaphylaxis!!

Dose dependent

• Can eat a certain amount before it triggers anything
• We are able to determine what their saturation point is- so they can tolerate small amounts

Food intolerance
- Pharmacological reaction to a chemical component of foods- symptoms similar to food allergy often more diffuse->eg. drowsiness, fatigue, irritability, muscle pain

Dose dependent

Question 25

Substances that provoke food intolerance

Answer 25

Not the protein, it is the chemicals naturally occuring in foods- that give food its colour and flavour!!

Question 26

Substances that provoke Food intolerances are:

Answer 26

Salicylates

Sulfites

Amines

Glutamate

Question 27

What are salicylates?

Answer 27

• Found naturally in many fruits, vegetables, nuts, herbs & spices, yeast extracts etc → hence elimination diets can be difficult as they will be restricted from these vital nutrients (especially in children)
o A true elimination diet is removing all these allergenic foods & adding them back in over time
• Aspirin

Question 28

What are sulfites

Answer 28

• Preservatives

* Alcoholic drinks, dried fruit & veg, processed foods & occasionally medication

Question 29

What are amines?

Answer 29

• Histamine, tyramine
• From protein breakdown
• Cheese, chocolate, wines, beer, yeast extracts, fish products
• Bananas, avocados, tomatoes & broad beans

Question 30

What are amines?

Answer 30

• Most clear
• An amino acid found in all proteins
• Glu in proteins → few problems
• MSG is often added to foods as a flavor enhancer (621) to some foods
• Ribonuclleotides!

Question 31

Enzyme deficiency

Answer 31

Lactase Deficiency

• Common, about 75% of the worlds adult humans lack lactase
o These numbers become really high in certain ethnic populations (asian, African populations) – unable to dugest lactose in milk properly
• Lactase (small intestine mucosa), digests lactose from milk
• Lactase activity decreases in adulthood
• Consume milk products → nausea, cramps, bloating, gas, diarrhea, within an hour or two
• Treatment: minimize lactose intake, by using low-lactose dairy
o Manage other nutrients!! Because you are removing dairy from the diet
o Crucial phase up to early 20s where need sufficient calcium

Question 32

The Outlier- Coeliac Disease

What is it?

What are the symptoms?

Answer 32

Autoimmune disease
• About 1% of Australians
• Abnormal response to gluten (found in wheat, rye & barley)
• Inflammation of small intestinal mucosa
• Symptoms can include intermittent diarrhea, abdominal pain or cramping, indigestion & weight loss (malnutrition in severe cases)
o We can test for it & diagnose appropriately
o Must replace these nutrients because removing gluten from the diet can fix this → dietary management
o Sauces still contain it

Question 33

How do you diagnose Food Allergy v. Intolerance?

Answer 33

• Skin prick test
• RAST – blood test for specific IgE
• Elimination diets
• Food/allergen challenge

Based on a combination of;
• CLINICAL HISTORY –
o Nature of the symptoms – pain, vomiting, rash → is it localized (if it is generalized then it will be more likely anaphylaxis)
o Time from onset – from when they consumed the food
o Nature of symptoms (urticaria, angioedema)
o Exposure to potential triggers
o Timing of reaction in relation to exposure (immediate rather than delayed)
o Response to treatment (antihistamine, adrenaline)
• Investigations
o Skin Prick Testing (SPT)
o Blood test for allergen specific IgE (formerly known as RAST)
• Medication supervised allergen challenge
• It is important to refer to clinical immunology/allergy specialist for assessment

Question 34

Diagnosis

Answer 34

Allergen Specific IgE Tets or RAST
• Comes first
• Quick, easy
• IgE positive – tells you they do have it- doesn’t tell you anything about the severity
• Blood tests help identify allergens – measure specific IgE
• Previously called radioallergosorbent test (RAST)
• Can help identify allergens – but not intolerance
• Will tell you if you do need to do skin pricks (as they are time intensive & difficult)
• Concentration of antibody has been correlated with likelihood of reaction

Skin Prick Testing
• Can help identify allergens – but not intolerance
• A panel of suspected allergens is injected into separate site in the skin
o Observe for “wheal & flare” reaction
• Size & significance of the whelt
• Pros: need to have consistent technique (same person); measure the size of the wheel gives indication of severity (useful for retesting – some food allergens such as wheat you do grow out of)
• Cons:
o High negative predictive value
o Lower positive predictive value depends on the wheal sieze
o Wheal diameters associated with 95% specificity for positive food challenge have been defined
o Appropriate allergens should be used:
• Commercial extracts
• Fresh foods as required
o SPT can be done for patients of any age, however is less sensitive in children less than 2 years of age
o Need a clear patch of skin – in a child with other atopic illnesses such as eczema this can be an issue

Elimination Diet
• Remove foods from diet that you consider to be the allergens, and then consider adding these back one by one
• Major downside → nutrient restricted diet (bad idea in kids unless significant symptoms)\

Food Challenge
• In kids with food allergy/anaphylaxis they do a medically supervised food challenge
• Gradually increasing the dose of food exposure
• Enable you to determine the actual response & to gage over time if there is a difference
• Good for determining severity of disease

Question 35

Management of allergic responses!

Answer 35

• Fundamental for anaphylaxis = an ACTION PLAN
o Has the child’s photo, common triggers, emergency contacts, signed off by doctor
o Annual review - because the allergy can change in a year
o How to use the epipens
• Adrenaline – dose, delivery devices
• 1st & 2nd line treatment
• Emergency protocols

Question 36

Adrenaline- explain

Answer 36

• Adrenaline is the first line treatment for anaphylaxis
Adrenaline acts to:
• Inhibit the release of inflammatory mediators
• Reverse the physiological effect of mediators by:
o Reducing airway mucosal oedema
o Inducing bronchodilation
o Inducing vasoconstriction (thus increasing HR & BP)
• There is huge increased membrane permeability : 50% fluid shift
o Increasing strength of cardiac contraction
• The maximum effects of adrenaline last 15-20 minutes, repeated doses may be needed

Question 37

Why is time the crucial element in treating anaphylaxis?

Answer 37

Difficulties
• Person with any/all of these symptoms may not have an allergy it may be another allergy or other condition
• Person with a food allergy do not usually show all of these symptoms
• People with a food allergy do not all react to the same allergen/s

More:
• Increasing vascular permeability during anaphylaxis can shift approx. 50% of vascular fluid to the extra vascular spaces within 10 minutes
• Mast calls may also promote plaque rupture (accumulate at plaque sites)

Death Timeline
•	Food: 25-25 minutes
•	Drugs (hosp): 5 minutes (IV)
•	Drugs (comm): 10-20 mins
•	Insect: 10-20 mins?

Question 38

Explain the Biphasic reaction that occurs in individuals who have recieved adrenaline

Answer 38

Observe patient for at least 4/8 hours after last dose of adrenaline
• Relapse, prolonged &/or biphasic reactions may occur
• Prolonged reactions may be observed by residual adrenaline after IMI
• Observe overnight if patient:
o Had a severe reaction (hypotension or hypoxia) OR
o Required repeated doses of adrenaline OR
o Has a history of asthma or biphasic reactions OR
o Has other concommittant illness OR
o Lives alone or is remote

BIPHASIC REACTIONS DEVELOP IN UP TO 20% of anaphylactic reactions

Question 39

How do you manage food allergy and intolerance?

Answer 39

• Most patients will need:
o To restrict or eliminate the food/s or food component/s that are causing the symptoms
• Dietetic advice crucial
o A) avoid nutritional deficiencies after key foods eliminated
o B) identify “hidden” forms of the guilty food or chemical
• Food labeling laws
o Require mentioning presence of foods & ingredients commonly causing food allergy
• Children may grow out of some types of food allergy & intolerances
o So abstinence may not be forever
• Usually permanent are:
o Allergies to peanut, nut, fish & shellfish
o Coeliac Disease
o Inborn errors of metabolism (autoimmune – hashimotos)