Hay fever and mould allergy

What is happening

Pollen and mould spores are both harmless to most people. In someone sensitised to them, the immune system has produced IgE antibodies against their proteins, and those antibodies sit attached to mast cells in the lining of the nose, eyes and airways. When pollen arrives, it binds to the antibodies already in place and the mast cells release the histamine they have stored. That release is what produces the sneezing, congestion, streaming and itching — the pollen itself does nothing. The mechanism is covered more fully under what an allergy is.

In the nose this is allergic rhinitis; seasonally, hay fever. In the eyes it is allergic conjunctivitis. In the airways it can set off asthma.

Which pollen, and when

There is no single pollen season. There are three, they overlap, and which one causes the trouble can usually be worked out from the calendar alone.

Tree pollen comes first, from late March to mid-May, and affects around a quarter of people with hay fever. Birch is the significant one in the UK.

Grass pollen runs from mid-May through July and is the one most people react to. It has two peaks in England and Wales: the main one from early June, and a second, lower peak in early July. Anyone whose worst weeks are reliably in June is almost certainly reacting to grass.

Weed pollen runs from around the end of June into September, though weeds can release pollen at almost any point. Nettle, dock and mugwort are the common sources here.

Symptoms that arrive in April and clear by May point to trees. Symptoms through June and July point to grass. Symptoms that persist into late summer and autumn point to weeds or to mould spores, which are discussed below. Knowing which matters, because it determines when treatment should start — and treatment started in advance works considerably better than treatment started once symptoms arrive.

What the weather does

Pollen counts are weather-driven, which is why some days in a bad season are fine and some days in a mild one are miserable.

Rain brings counts down. Rain that is early, heavy or prolonged keeps them low for the rest of the day, while a shower in the afternoon has much less effect. Grass pollen peaks on dry days with low humidity, a maximum temperature somewhere between about 18°C and 28°C, and a gentle breeze. Above roughly 28°C counts actually fall, and several hot days running can exhaust the supply.

Wind matters in both directions: a light wind barely lifts pollen off the ground, while a strong one disperses it thinly. Birch pollen, by contrast, needs moderate to high wind to travel. Prolonged cloud reduces how much pollen plants produce in the first place.

Because all of this changes day to day, the daily pollen forecast is more use than any rule of thumb. Counts are generally at their highest as pollen is released and lifted during the morning, and often rise again in the early evening as the air cools and pollen settles back down — but the forecast is the thing to check.

Reducing exposure to pollen

None of this is a substitute for treatment, and the effects are modest, but they are free.

Keeping windows shut on high-count days helps, particularly overnight and in the bedroom. Showering and changing clothes after being outdoors removes pollen that would otherwise be carried around the house and onto the pillow. Drying washing outdoors on a high-count day brings pollen indoors on the clothes and sheets, which is worth avoiding during the relevant weeks.

Wraparound sunglasses keep a useful amount of pollen out of the eyes, and a wide-brimmed hat keeps it off the face and out of the hair. Smoking makes symptoms worse.

Filtration is often suggested and is worth keeping in proportion — the benefits of home air purifiers are real but modest, and depend a great deal on the specific allergen.

Mould is a damp problem

Indoor mould grows wherever there is persistent moisture, and the mistake in most advice about it is treating the visible mould rather than the water feeding it.

Cleaning mould off bathroom tiles is worth doing, but if the cause is condensation forming on cold surfaces, poor ventilation, or a leak, it will return. The things that actually reduce it are ventilation and warmth: extractor fans used while cooking and bathing, windows opened afterwards, keeping cold rooms from getting cold enough for condensation to form, and not drying washing on radiators in an unventilated room. A dehumidifier helps where damp is persistent. Where the damp is structural — rising damp, a failed roof, penetrating damp through a wall — it is a repair, and in rented housing it is the landlord's responsibility.

When removing mould, it is better not to brush or vacuum it dry, since that disperses spores into the air. Damp cleaning, with the room ventilated, is the safer approach.

Mould is not only indoors. Spores from rotting vegetation, leaf litter and compost rise through late summer and autumn, which is one reason hay fever symptoms that persist past the grass season are not necessarily still grass. Someone who feels worst in September and October, or when gardening and clearing leaves, may be reacting to mould rather than pollen.

Treatment, in the order that works

A pharmacist can advise on all of the following without an appointment, and most hay fever is managed this way.

Antihistamines help with sneezing, itching and a runny nose, and less with a blocked one. The non-sedating ones — cetirizine, loratadine, fexofenadine, acrivastine — are the sensible default. The older sedating ones, including chlorphenamine and diphenhydramine, cause real drowsiness and impair driving, and brand names are no guide here: the same brand can contain quite different ingredients in different countries, so the generic name in the small print is what to read. There is little evidence that any one antihistamine beats another, and people often try two or three. Where the start of the season is predictable, beginning two to four weeks beforehand works better than waiting.

Steroid nasal sprays are the most effective treatment for hay fever, and the one most often abandoned prematurely. They are preventive rather than on-demand, and they need days to weeks of daily use to reach full effect — so a two-day trial proves nothing. Starting one to two weeks before symptoms are expected gives the best protection. Technique matters: aim outwards, towards the side of the nose rather than straight up, and the spray should not be dripping out of the nose or running down the back of the throat. Where symptoms stay poorly controlled, a spray combining a nasal steroid with a nasal antihistamine works better than either on its own.

Eye drops treat the itching and watering directly, and antihistamine drops are available over the counter.

A saline rinse — salt water through the nose, as a spray or a solution — clears pollen from the nasal lining and costs almost nothing.

Oral steroids can bring a severe season under control but are prescription medicines with effects throughout the body, used briefly and under supervision. They are not an everyday option and do not belong in the same list as the treatments above.

Hay fever and asthma

This is the part that makes hay fever more than an inconvenience. It can trigger asthma attacks and worsen other lung conditions, which is a reason to treat it properly rather than put up with it.

Anyone with asthma should keep a reliever inhaler to hand through the pollen season and use it as soon as symptoms worsen. Where asthma is involved, hay fever that is not under control is worth a GP appointment rather than another month of tablets.

When fruit suddenly causes trouble

Some people with pollen allergy find that certain raw fruits, vegetables and nuts make the mouth itch. This is pollen-food allergy syndrome, once called oral allergy syndrome, and it happens because the proteins in those foods resemble the pollen proteins closely enough for the same antibodies to recognise them.

Birch pollen allergy is the usual starting point, cross-reacting with apple, pear, cherry, peach, plum, apricot, almond, hazelnut, kiwi, celery, carrot and raw potato. Grass pollen allergy can cross-react with melon, watermelon, tomato, orange, kiwi and peanut. Mugwort allergy tends to involve celery, carrot, mango and some spices.

The symptoms are typically confined to the lips, mouth and throat — itching, tingling, mild swelling — appearing within five to ten minutes and settling within half an hour. Cooking changes many of these proteins, which is why cooked apple is usually fine when raw apple is not. That does not hold for peanuts, other nuts, soya or celery, whose proteins survive heat.

Severe reactions are uncommon, affecting something in the order of one or two per cent of cases, but they are possible, and anything beyond mouth and throat symptoms — hives elsewhere, vomiting, difficulty breathing, faintness — means a proper assessment rather than reassurance. It is also worth not assuming: a reaction to a food is not automatically this, and testing read alongside the history is how the two are told apart.

When to get help

A pharmacist first, for almost everything above.

A GP where symptoms are not controlled despite using a steroid nasal spray properly for several weeks, where they are interfering with sleep, work or school, where asthma is involved or breathing is affected, or where it simply is not clear what is causing them — autumn symptoms in particular can be pollen, mould or house dust mite, and guessing wrongly means treating at the wrong time of year.

Where symptoms persist despite proper treatment, a GP can refer on for assessment and, in some cases, for immunotherapy, which is the one treatment that addresses the allergy itself rather than its symptoms. It is a specialist service and is not available everywhere. The broader range of options is covered under managing allergies.