Hazelnut and Cross-Reactivity: Help patients understand their hazelnut allergy and symptoms due to cross-reactivity
Sophie, an 8-year-old girl with a history of rhinitis and oral allergy syndrome (OAS), visits her healthcare provider following a recent emergency admission after developing severe angioedema. Sophie recovered well after administration of antihistamines and oral steroids; she did not require epinephrine. Her mother reported that she had muesli containing hazelnut before the onset of symptoms.
She was previously tested for sensitization to respiratory allergens and was diagnosed with birch pollen allergy. Her healthcare provider conducts a full clinical history and physical examination and decides to test using hazelnut components.
After eating a bowl of cereal, 8-year-old Sophie was covered in large hives. What did specific IgE blood testing reveal?
Patient History
Family History
- Atopic father
Sophie's Personal History
- Sophie has had on-going mild allergic symptoms for six years.
- When she was 1 year old, she had milk allergy, which she has now outgrown.
- Sophie has suffered from rhino-conjunctivitis during spring and early summer for the last couple of years and she has had oral symptoms from eating hazelnuts. She was previously tested and subsequently diagnosed with birch pollen allergy.
Sophie's test results were:
Test |
Type |
Sophie's Results |
Birch |
Whole Allergen |
+3 |
Hazelnut |
Whole Allergen |
+2 |
Sophie had a negative skin prick test to grass, mugwort, cat, dog, and mite.
Test |
Type |
Sophie's Results |
Birch |
Whole Allergen |
3.4 |
Hazelnut |
Whole Allergen |
0.6 |
Based on history, evaluation, and testing, her previous healthcare provider recommended that Sophie use oral antihistamines during birch pollen season. It’s also recommended to avoid hazelnuts, as the symptoms indicate cross-reactivity between pollen and hazelnut.
Sophie's ImmunoCAP Test Results
These results together with this patient's case history and symptoms, help confirm the diagnosis.
Test |
Type |
Sophie's Results |
Hazelnut |
Whole Allergen |
3.9 |
Birch |
Whole Allergen |
5.3 |
Cor a 1 |
Allergen Component |
2.2 |
Cor a 8 |
Allergen Component |
<0.1 |
Cor a 9 |
Allergen Component |
1.3 |
Cor a 14 |
Allergen Component |
2.0 |
Bet v 1 |
Allergen Component |
4.5 |
Differential Diagnosis
Sophie’s severe reaction could be explained by her sensitization to the storage proteins Cor a 9 and Cor a 14, which shows that Sophie has a primary hazelnut sensitization to proteins that can cause severe and systemic reactions.1
Sophie’s birch allergy also gives rise to cross-reactivity with the PR-10 protein Cor a 1 in hazelnut.2
REFINED DIAGNOSIS
- Primary hazelnut allergy and birch allergy.
HEALTHCARE PROVIDER MANAGEMENT PLAN
- Sophie's healthcare provider referred her to a dietitian for help in adjusting her diet.
- Sophie was advised to strictly avoid hazelnuts and always carry her emergency epinephrine autoinjector.
- Sophie's healthcare provider arranged follow-up education and training on autoinjector use for Sophie and her family.
- Sophie was advised to continue to use antihistamines for the birch pollen symptoms, starting treatment two weeks before the season.
FOLLOW UP
- Sophie is seen by her healthcare provider one year later. She has had no further episodes and is fit and well. Her autoinjector technique is satisfactory.
The people, places, and events depicted in these case studies and photographs do not represent actual patients, nor are they affiliated in any way with Thermo Fisher Scientific.
- Blankestijn MA, Knulst AC, Knol EF, et al. Sensitization to PR-10 proteins is indicative of distinctive sensitization patterns in adults with a suspected food allergy. Clinical and Translational Allergy. 2017;7:42. doi:10.1186/s13601-017-0177-4.
- Masthoff LJ, et al.: Sensitization to Cor a 9 and Cor a 14 is highly specific for a hazelnut allergy with objective symptoms in Dutch children and adults. J Allergy Clin Immunol. 2013
