Hundreds of different allergens have been identified, and can be classified by similarities in structure/genetics, usually based on the plants being related to each other in evolutionary terms.
This is useful because cross reactivity is more common, the more closely different proteins are related. Not all are allergenic however, and not all cross react.
You can also predict how heat stable these proteins are by how cross linked their structure is. Linear proteins are more easily disrupted by heat, so the allergy is likely to only be an issue with raw (or frozen from raw).
Most allergens belong to one of a small number of groups:
- PR-10 eg Bet v 1, Ara h 8, Cor a 1, Pru p 1, Mal d 1. Heat labile, homologous. Most pollen food syndrome cases (birch pollen).
- Profilin eg Bet v 2, Cor a 2. About 20% of pollen food syndrome cases. More common in Southern Europe – birch and oak too, but also olive tree, London plane, grasses, ragweed.
- Prolamin – includes nonspecific lipid transfer proteins (nsLTP) which are heat stable but very cross reactive, and are found in fruit, vegetables, nuts, legumes, seeds and cereals, as well as plane trees and mugwort. Best known is Pru p 3, which is a good surrogate marker for any nsLTP sensitisation, even if cherry (prunus) isn’t a known issue. Ara h 9, Cor a 8, Mal d 3.
- Cupin – includes legumins. Heat stable. Ara h 1 and 3, lentil, cor a 9/11 (hazelnut), some soya.
- Thaumatin – named after W African shrub! Various fruit including apple, kiwi, plus cedar pollen.
- 2S albumin eg Ara h 6.
Glasgow lab offers only hz, peanut, peach/cherry, egg (Gal d 1), alpha galactose and bee/wasp.