Ingredient decoder
Hazelnut
Hazelnut is a birch-pollen cross-reactive food — its PR-10 Proteins protein resembles the birch allergen closely enough that pollen-allergic people can react to it.
Allergen family data
| Family | Category | Severity | Mapping |
|---|---|---|---|
| PR-10 Proteins | pollen_food | Usually mild (oral allergy syndrome) | Curated mapping |
Sources: SleuthIt curated dataset
Also appears as
Cross-reactivity
~70% of birch pollen allergics react to raw apple
~50% of birch allergics react to cherry
Birch-celery-mugwort-spice syndrome
Case notes
Filbert is the name that trips people up most often. It appears in ingredient lists, baking mixes, and confectionery descriptions as if it were a distinct nut, but filbert and hazelnut are the same thing — Corylus avellana. If you're scanning a label for the word "hazelnut" alone, filbert can slide right past you. The same goes for the botanical name Corylus avellana, which shows up on specialty and imported products, and for Cor a 1, the protein designation you may see referenced in allergy testing paperwork rather than on packaging.
There's a second reason hazelnut is easy to overlook, and it has nothing to do with spelling. Hazelnut carries a PR-10 protein, the same family that includes the birch pollen allergen Bet v 1. That protein similarity is why some people with birch pollen allergy react to foods they never connected to their symptoms — roughly 70% of birch pollen allergics react to raw apple, about 50% react to cherry, and celery is part of the same birch-celery-mugwort-spice pattern. PR-10 reactions are usually mild, typically presenting as oral allergy syndrome.
PR-10 proteins are also heat-sensitive, which is why a food may cause symptoms raw but not after cooking or processing. For label reading, the practical takeaway is to treat filbert, Corylus avellana, and hazelnut as one entry on your list, and to note the form a food takes — raw versus processed — alongside the ingredient name when you're tracking what happened.
Questions
Hazelnut is a birch-pollen cross-reactive food — its PR-10 Proteins protein resembles the birch allergen closely enough that pollen-allergic people can react to it.