Hay fever

=allergic rhinoconjunctivitis due to seasonal triggers, typically grass and/or tree pollen. First described by John Bostock in 1819! More likely if born in early months of year!

So itchy, swollen, watery eyes, runny and/or blocked nose, sneezing. Often itchy throat and ears too. Cobble stone appearance can be seen at the back of throat.

Not dangerous, but can seriously affect quality of life: poor sleep, poor concentration (exams usually at worst time of year), embarrassment about snot. One study showed children in England were less likely to get their predicted exam grades if they had hay fever, especially if prescribed sedating antihistamines. Moderate to severe hay fever also associated with worse, uncontrolled asthma. London study found hospital admissions for asthma 50% higher 3 days after high grass pollen levels (inconclusive for tree pollen). [Int J Biometeorol. 2017] Brussels study found similar, compounded by air pollution. Treatment of hay fever with intranasal steroids or class 2 antihistamines reduced admissions by up to 80%. [asthma res and pract 2015]

Associated with other atopic conditions, such as food allergy and asthma. Under recognized as trigger for asthma exacerbations – pollen is too large to trigger the lower airways directly, rather, pollen exposure in the upper airways trigger inflammation that travels down (probably over a period of weeks) to the lower airways. An exception is when pollen grains are fragmented, as seen in thunder storm asthma where one night in Melbourne, 2016, several thousand acute respiratory presentations came to ED (up over 400%), ambulance service was overwhelmed, hospitals ran out of inhalers. 10 deaths implicated. [Australia, Clin Exp Allergy. 2018;48:1421‐1428]. Complex though, rain/moisture probably contribute to pollen grain rupture, and atmospherics bring surges of pollen down to ground level.

There are many different species of grass, but if allergic to one you tend to be allergic to all of them. Trees on the other hand vary, you tend to be allergic to specific groups of trees. In Europe the most important are birch (northern Europe) and olive (Southern Europe). Birch is related to alder, hazel, beech and oak.  Olive is related to ash.  Weeds belong to various unrelated families.

Hazel trees can start producing pollen in January! Weeds such as nettle can continue producing pollen through September! Moulds seem more associated with asthma than hay fever. Cypress blooms in winter! 

Pollen seasons in Scotland – University of Worcester Pollen Lab

It’s not just pollen count – the amount of allergen carried by the pollen (“pollen potency“) varies too. Correlates pretty closely but varies by time and place, 4-5 fold difference geographically (especially grass). France has the highest yearly average grass pollen potency, 7-fold higher than Portugal. Olive pollen from two locations 400km apart varied 4-fold in their allergen potency – in Portugal there are times when pollen from Spain probably more of a problem for triggering hay fever than pollen from “local” trees! [Health Impacts of Airborne Allergen Information Network (HIALINE project)]

Management

Watch the pollen count, and choose activities inside or outside accordingly. There are apps that can help with this. But note that the time of day is important too – for grass pollen, the risk is greatest in the first half of the morning and again from about 4pm in the afternoon, until late evening. But can persist into the early hours if temperatures remain high, this effect is particularly noticeable in the cities of the south of England. For tree pollen, the risk is usually during daylight hours only.

Closing windows, or at least not sitting near windows should help. Wash your hair more regularly. Don’t dry clothes outside. Pollen barrier balms available (evidence?). Big, wrap around sunglasses?

Choose when and where you are going on holiday carefully, so you get away during the worst period. North of Scotland and the islands have a short, late grass season (late June, early July). Coastal areas likely to be best (although often there are fields just back from the coast, so it may depend on the wind direction!). For tree pollen, season is earlier for most (see above), and there are parts of Scotland (Orkney, Lewis, Caithness, Sutherland) with very few trees. For holidays abroad, see World pollen data.

Antihistamines – oral or nasal. Various, some people find one works better than another Sedating antihistamines eg Chlorphenamine should be avoided except at night. Nasal steroids useful if used correctly. Combination steroid/antihistamine available. Leukotriene receptor antagonist licensed for hay fever in children with asthma.

Short courses of oral steroids might be justified for special occasions.

Immunotherapy available – deaths reported in asthmatics with poor control.

Sublingual – age not important cf ability to hold in mouth for 2 minutes. Not approved by SMC in Scotland yet. Combined grass and house dust mite coming.

[Sian Ludman, St Mary’s]

For symptoms all year round (perennial), triggers such as house dust mite and pets are more likely.

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