Peanut Allergy Course - AAAI

Diagnosis and natural history of peanut allergy 

Prevalence of peanut allergy has doubled over the last ten years

1% children \.6% adults 

Peanut allergy generally persists into adulthood\

Peanut is one of the leading causes of anaphylaxis
& death from 
food allergy

How to diagnose? 

1- Detailed history 

*may indicate a clinically significant reaction from known peanut exposure

*will provide the basis for interpretation of diagnostic test results

*may show that the individual is at high risk 

*a strongly suggestive history may be virtually diagnostic for peanut allergy

suggestive history of peanut allergy:

Timing:

The majority of reactions occur
within 20 minutes.  Nearly all reactions occur
within 2 hours of exposure.

Reproducibility:

Reactions should be reproducible with subsequent exposures.

Symptoms:

90% cutaneous manifestations

Non-dermatologic manifestations associated with more severe reactions:

• oropharyngeal itching

     and throat tightness

• coughing
• wheezing
• nausea/vomiting
• diarrhea  tacycardia 

other comorbid conditions: 

• Asthma
Atopic dermatitis
• Other allergic conditions
• 
  

Diagnostic tests after history:

Skin Prick Testing (SPT) - the first method

In Vitro Specific IgE Testing

Oral Food Challenge (OFC) if indicated

SPT:

A positive
skin test alone 
does not make the diagnosis.

8% of the US population will have a positive SPT to peanut, but only ~1% are truly allergic

It is essential to interpret SPT test results in light of the patient history.

with a negative test : negative predictive value: 97%

The probability of peanut allergy increases with wheal size

95% positive predictive value:

wheal > or equal 8 mm 

Invitro specific IgE testing : 

Confirmatory in vitro specific IgE testing may be necessary after SPT
if results are equivocal or negative with a strong clinical history

The probability of peanut allergy increases with higher levels of peanut-specific IgE

With a
convincing 
history,
a peanut-specific 
IgE > 14 kU/L

has 95% p

An undetectable specific IgE level (≤0.35kU/L) does not rule out the possibility of peanut allergyositive

20% of
peanut allergic individuals have undetectable specific
IgE 

Oral food challenge

 is a gold standard for diagnosis of peanut allergy 

should be used if the diagnosis is uncertain after history, SPT, IgE

should also be used to confirm resolution of allergy 

OFC should always be physician-supervised in a facility equipped to handle anaphylaxis.

Quality of life often improves after OFC even if a patient fails the challenge

Risk factors for persistent peanut allergy:

Larger wheal size at initial diagnosis

Increasing wheal size during the first years after initial diagnosis

Higher levels of peanut-specific IgE at the time of diagnosis

Increasing levels of peanut-specific IgE over timedictive value

severe reactions: GI manifestations, anaphylaxis 

concurrent atopic conditions:,atopic rhinitis 

additional nut allergies 

30% of peanut allergic are allergic also to tree nuts 

spontaneous resolution of peanut allergy:

20% of allergic children will tolerate peanut by age 8 years 

children with peanut allergy should be periodically evaluated for resolution

there is a greater likelihood for resolution of allergy for children: with small wheal size  and/or low levels of peanut-specific IgE at the time of diagnosis and who continue to have low levels in subsequent years.

those children should be evaluated regularly 

If there is a
significant likelihood 
that a child has outgrown peanut allergy,

a physician-
supervised OFC
should be
pursued.

Risk factors for recurrence:

can recur in 8%  of the individulas 

Patients who have passed an OFC should still consider carrying an epinephrine auto-injector in the event of recurrence.

the risk for recurrence is greater in children who continue to avoid peanut after resolution of allergy 

children who have passed OFC should keep peanut in their diet