Oral allergy syndrome

Used interchangeably with Pollen food syndrome, refers to patients who report only oral symptoms.

Pollen Food Syndrome (PFS) refers to fruit and/or nut allergy, associated with birch pollen allergy (ie hayfever).  The fruit allergy however is usually mild, eg itching/tingling of lips/tongue only.

Due to cross reactions with similar proteins found in fruit (particularly those with pips inside and a peel eg apple, pear, peach, plum, cherry).   This group of fruit is known as Rosaceae.

You may find that you can eat the fruit if peeled, tinned, cooked or processed (eg jam). The ripeness, even the specific species, can matter too. Some affected individuals even put up with the itching because they prefer not to miss out on their favourite fruit!

Often emerges in adulthood. Only described in 1942! Seen in up to 25% of kids. Partial binding by IgE. Big variations geographically eg S Europe cf UK.

The main impetus for making the diagnosis is to select patients with a lower risk of anaphylaxis, even if nut allergic.  However, not always possible, and certainly not 100% reliable.  People who have primary IgE mediated allergy will of course also report oral symptoms only if low dose exposure.  In the original description of oral allergy syndrome, 50% progressed to systemic reactions.

So, important to differentiate –

  • primary IgE allergy who have only had oral symptoms so far (but are are risk of severe reactions, due to sensitisation to storage proteins, typically found in seed/kernel)
  • benign PFS, where allergic to Bet v 1, its homologues (eg Ara h 8, Cor a 1 – see peanut allergy) or other PR-10 or Profilin.  These proteins are usually in the pulp of the fruit.
  • PFS with potential for systemic reactions where allergic to LTP (typically found in the peel)

But there are reports of anaphylaxis to peanut despite being exclusively Ara h 8 sensitised and passing an oral challenge – but had big dose on empty stomach! [https://doi.org/10.1111/cea.12425]

Prick to prick tests – get skin and pulp!

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