PFS: What is it and what do we need to do about it?

Gemma is 28 and is worried her allergies are worsening. Her spring time hay fever is worsening and she was eating some kiwifruit the other day (one of her favourite fruits) and she started developing itching of her mouth and throat and her lips swelled a little. She also mentions that her hands get itchy when she peels potatoes. She’s asking for allergy testing and/or a referral to the allergy clinic. So what is going on with Gemma? Do we need to refer to the allergy clinic? It’s a nine month wait…do we even need to consider an adrenaline auto-injector?

Sneezy season is upon us. The lambs are jumping, the ducklings are swimming, and the trees are spewing all manner of pollens for poor hay fever sufferers. A quick look at the Met forecast shows the pollen count to be high or very high through most of the UK for most of this week. A surprisingly common condition associated with the upcoming hay fever season is Pollen Food Syndrome (PFS). I was vaguely aware of this condition (AKA oral allergen syndrome) but was very uncertain as to how serious the condition is, and what we should do as GPs. Luckily The British Society for Allergy and Clinical Immunology (BSACI) have produced recent guidance on this condition in 2022, with a very helpful GP specific section. And as it turns out this qualifies (for me anyway) as a great GP condition - it can be diagnosed in most cases on history alone (tick), no fancy tests needed (tick), and can be managed with simple measures and advice (tick, tick). 

So what is PFS?

PFS is a common (estimated prevalence in the UK ~2%) IgE mediated food allergy caused by a cross reaction between pollens (usually tree) and raw plant food allergens. In PFS the immune system is sensitised by pollens and then the person develops an IgE reaction to plant food allergens, which in their raw form are structurally similar to the pollens. The main pollens involved are birch, but also hazel and alder, and thus PFS usually develops in people with spring or summer time hay fever. The associated food triggers are widespread but common ones include stoned fruit (cherries, plums, peaches), other fruits (kiwifruit, pear, tomato), vegetables (celery, carrot, potatoes and other root veg) and some nuts (hazelnut, almonds, walnut, peanuts) and soya products. It’s important to note that it is only raw foods that trigger PFS - cooking denatures the food allergens. 

So what symptoms do people with PFS get?

After ingesting the raw food, people get immediate (within 10 minutes) mild itching/swelling of the oropharynx which resolves spontaneously over 30-60 minutes without treatment, but can be eased with oral antihistamines. Peeling raw veg can cause itchy hands. 

Do we need to do any tests or refer to the allergy clinic? 

In the vast majority of cases no (but see caveats below). As the BSACI state ‘The diagnosis and management of PFS can often be wholly managed in Primary Care’. If the person reacts only to raw fruits, veg or soya, has typical mild symptoms with a background of spring hay fever, we can manage PFS in primary care without further tests r referrals. The BSACI leaflet has a good simple flow chart for us to follow. 

What advice do we give people with PFS?

They should simply avoid only those raw foods that have provoked symptoms. We should provide more detailed information (good info from Allergy UK here), and we should optimise any associated co-morbidities, especially rhinitis and asthma. If symptoms are unpleasant they can take an oral non-sedating antihistamine. We should obviously safety net to return if they start developing any symptoms that would need an onward referral (see below). 

When do we need to refer?

Anyone who has severe symptoms (e.g. throat closure) or systemic symptoms needs referral to an allergy clinic, as does anyone who has reacted to nuts (even if the symptoms are mild) or cooked fruits/veg. If the person has multiple food triggers or there are concerns about an already limited/compromised diet we should consider referral to a dietician.

What about an adrenaline auto-injector (AAI)?

The majority of people with PFS do not need AAIs. If however they have had severe reactions, especially if they have concurrent asthma we should prescribe an AAI whist awaiting allergy clinic review, although in some cases the AAI may be discontinued by the allergy clinic. 

So Gemma has a typical picture for PFS, her symptoms are mild and they settled within 30 minutes. She doesn’t need any further tests or referrals, or an AAI, which she’s pretty relieved about. She just needs some simple advice and direction to further information on the condition and some optimisation of her hay fever. Another happy customer (tick).