Food Allergy the nuts and bolts

1
Food Allergy the nuts and bolts

• Tom Gerstner, MD, FRCPC
• Section of Allergy Clinical Immunology
• Dept. of Pediatrics and Child Health
• University of Manitoba

2
Definitions

• Allergy (hypersensitivity)
• IgE mediated
• non-IgE mediated

• Adverse reaction

Intolerance non-immune toxic pharmacologic
al metabolic psychogenic
3
Clinical spectrum of food allergy

• Anaphylaxis multisystemic
• Food associated, exercise induced
• GI
• Immediate emesis, diarrhea, cramps, part of
  anaphylactic response
• GER
• Oral allergy syndrome
• Food protein induced enterocolitis
• Allergic eosinophilic syndromes
• Food protein induced enteropathy, celiac disease
  (gluten sensitive enteropathy

4
Clinical spectrum of food allergy

• Cutaneous
• Urticaria immediate
• Atopic dermatitis more delayed
• IgE and cell mediated
• Respiratory Rarely occurs in isolation
• allergic rhinoconjunctivitis
• asthma
• Major risk factor for life threatening food
  allergy
• Conversely, food allergy a risk factor for more
  severe asthma

5
The scope of the problem

• Reported food intolerance 12-35
• Recent estimates 11.4 million Americans, or 4 of
  population, have food allergy
• 10 years ago, less than 1
• Higher prevalence in children
• 6 population affected less than 4 years
• Recent US, UK data suggest doubling incidence of
  peanut allergy over last decade

6
The scope of the problem

• Childhood
• 90 of hypersensitivity reactions are due to
  milk, eggs, peanuts, nuts, soy, and wheat
• Adults
• 85 of hypersensitivity reactions due to peanuts,
  fish, shellfish, and tree nuts
• More diversified diet has resulted in an increase
  in allergic reactions to other food, including
  fruits (kiwi) and seeds (sesame)

7
Prevalence of Food Allergies in the U.S.
Sampson, 2004
8
Diagnosis

• HISTORY
• 1. Define IgE vs non IgE mediated
• 2. Suspected food(s)
• 3. Symptoms
• 4. Time course
• 5. Quantity
• 6. Reproducibility
• 7. Presence of other factors
• 8. The length of time since the
  last
  reaction

9
Diagnosis

• 2. DIET DIARY
• 2 weeks, prospective record
• intermittent symptoms record exposures in
  previous 12-24 hours
• 3. ELIMINATION DIET
• 2 weeks
• basis of history, symptom diary
• SPTs or RASTs
• confounding factors
• a more strict 2 week elimination diet may be
  warranted elemental diet

10
Diagnosis Prick Skin Tests (PST)

• severe acute reaction to suspect food (e.g. acute
  urticaria, swelling, respiratory distress)
• atopic dermatitis-moderate/severe and not
  responding to medications
• chronic relapsing gut symptoms
• high expectation of negative result
• follow-up on a previously diagnosed food allergy

Indications
11
Diagnosis Prick Skin Tests

• Disadvantages
• lack of standardization
• Positive predictive value 50
• presence of specific IgE may be without clinical
  relevance
• does not help with non IgE-mediated reactions

• Advantages
• gt95 negative predictive value
• direct food challenges/elimination diet
• 2 studies
• 1. Hill, 2001
• SPT to milk egg peanut with wheal diameters gt8mm
  more than 95 predictive of clinical reactivity
• 2. Kagan, 2003
• PST gt5mm 100 sensitivity
• Positive predictive value only about 50

12
Diagnosis CAP RAST

• Pharmacia CAP RAST
• quantitative assay of food specific IgE
  antibodies,with improved predictive value
• range of 0.35-100,000kU/L
• Sampson, 1997
• food specific IgE provided increased PPV for egg,
  milk, peanut, and fish

• Less sensitive than PSTs
• May be preferred in certain situations

13
Diagnosis Predictive value of food specific IgE
levels
14
Diagnosis Oral food Challenges

• Open
• foods implicated by lab results, but unlikely to
  be clinically relevant
• Single blind
• Double blind placebo controlled
• The gold standard for the diagnosis of food
  allergy

15
Diagnosis Oral food Challenges

• What DBPCFCs have taught us
• most case histories are inaccurate
• short list of foods in 90 of cases
• most kids allergic 1-2 foods
• reproducible food-induced symptoms confined to
  the GI tract, skin, and airways
• asthmatic and rhinitis symptoms rarely occur in
  absence of other symptoms

16
Food Allergy Prevention

• Conclusions
• Current recommendations
• High risk infants
• Exclusively breast fed
• Lactating mothers avoid peanuts, nuts
• Introduction of solids delayed until 6 months,
  eggs for 18 months
• Major allergens such as peanuts, nuts, fish and
  seafood be introduced after age 3

17
Natural history

• Egg
• 60-80 of infants with egg allergy are tolerant
  of
  egg by 5 years of age
• High risk for development of asthma later in life
• Milk, Soy
• Enterocolitis
• Vast majority become tolerant within 2 years
• IgE mediated
• Host A. 1994 Prospective study of milk
  hypersensitivity in children infancy through
  3years
• Outgrown
• 50 by age 1 year
• 70 by age 2 years
• 85 by age 3 years
• 3-4fold increase risk of developing asthma or AD
• Allergen avoidance appears to hasten development
  of tolerance

18
Natural History of Peanut Allergy

• Resolvers (20)
• Milder initial reaction
• Initial reaction lt 5 years
• less allergic to other foods
• lt6mm wheal on PST
• much less likely to have asthma or other nut
  allergy
• SPT predicted reactivity but not severity

19
Treatment avoidance

• Patients dont react to peanut fumes
• Simple washing and wiping techniques effective to
  eliminate residual peanut
• Education of patient and parents
• Reading labels, avoiding high risk situations
• Hidden ingredients (eg peanuts in sauces and
  eggrolls)
• Cross contamination
• Buffets, peanut butter in home
• School management plans
• Early recognition of allergic symptoms
• Early management of a severe reaction

20
Treatment Epipen

• Jr (.15mg) and regular (.3mg)
• lt25kg Jr
• gt30kg regular
• for anyone with a reaction to peanuts, nuts,
  seafood, seeds
• anyone with a serious reaction to milk, egg,
  kiwi, banana, carrot ect...
• Delayed use associated with poor outcomes
• Instruct on its use! Review!

21
Treatment Acute

• Antihistamines
• Oral allergy syndrome
• Skin manifestations
• No systemic effects
• Adrenaline (IM)
• Short acting bronchodilators
• Systemic corticosteroids
• May protect against protracted or late phase
  anaphylaxis (biphasic)
• IV fluids, respiratory support, inotropic agents,
  H2 blockers
• Observe in ER for 6 hours

22
Novel approaches for treatment of food allergy

• Anti-IgE therapy
• Immunostimulatory oligonucleotides
• Peptide immunotherapy
• DNA based therapies
• Probiotics
• Cytokine therapy
• Chinese herbal medicine
• One shown to block anaphylaxis in mice

23
Food additives and behaviour

• Feingold, 1970s
• attributed 50 of hyperactivity and impulsive,
  disruptive destructive behaviour to food
  additives
• subsequently, a number of DBPC studies were
  conducted that refuted these reports
• food additives NOT considered to play a role in
  cognitive/behavioral alterations

• Sugar
• controlled trials have failed to demonstrate any
  significant change in children's behaviour or
  cognitive function attributable to ingestion of
  sugar, or aspartame (Wolraich, NEJM, 1994 Mahan,
  Ann Allergy,1988)

24
Food additives-conclusion

• Some suggestive evidence linking tartrazine and
  worsening control of chronic urticaria (in
  adults)
• subset of asthmatics may react to sulfites
• despite the popular phobia of food additives, and
  the obsession for so-called natural organic
  foods, the greatest dangers come for naturally
  occurring foods