WHO, WHAT, WHY?
The Magazine answers...
Hay fever season is well under way, meaning misery for millions of people across Britain. But why are some people suddenly struck by the condition after years of experiencing no symptoms?
With pollen counts soaring, hay fever sufferers are in the midst of their annual bout of summer misery.
But although the condition is generally assumed to begin in childhood, some adults will be getting a nasty shock as they experience unpleasant symptoms such as sneezing and itching for the first time.
Despite plenty of research, no-one really knows
It could be that something in the environment of those with a genetic predisposition to allergies that sets it off
Alternatively, sufferers possibly experience very mild symptoms that they do not notice as children
Unfortunately, there is no way to predict when people who are atopic - that is, genetically predisposed towards allergies - begin to show signs that they are sufferers, says Beverly Adams Groom, chief palynologist at the National Pollen and Aerobiology Unit at the University of Worcester.
But broader theories about whether pollution or, conversely, a more sanitised environment could be causing a rise in hay fever symptoms could offer a clue.
"Lots of people assume that everyone with hay fever develops it in childhood, but we've had people coming to us in their 70s who've just been diagnosed," says Ms Adams Groom.
"People who have a genetic disposition are going to develop it, but as to what triggers it we don't know."
The bee may love pollen... but hay fever sufferers certainly don't
Hay fever is an allergy to pollens - the male reproductive parts of plants - from grasses and trees.
When these come into contact with the tissue inside the nose, they trigger an immune reaction that can cause congestion, sneezing, itching, and a runny nose.
Between 15 and 20% of people in the UK are thought to be affected, with the numbers being even higher among teenagers and symptoms typically peaking in people's 20s.
However, not all follow this pattern, and Ms Adams Groom suggests this could be linked with whatever is driving the general rise in hay fever cases.
Allergy specialist Prof Stephen Durham has calculated that the number of sufferers has doubled over a 20-year period.
"There's some evidence that pollution exacerbates it," he says. "And you've also got the hygiene hypothesis - that our bodies aren't as strong because we aren't exposed to infections when we are small children that our systems rebel against."
Oddly, researchers in Austria have also found that young children in regular contact with farm animals are less likely to develop allergies later in life.
WHO, WHAT, WHY?
A regular part of the BBC News Magazine, Who, What, Why? aims to answer some of the questions behind the headlines
Children living on farms were found to be three times less sensitive to hay fever and nearly four times less likely to suffer from asthma than those living in a non-rural environment.
This all may suggest that something about modern lifestyles may be responsible.
But, as Brian Lipworth, professor of allergy and respiratory medicine at the University of Dundee says, not enough work has been done to be sure either way.
However, he suggests that it could just be that many supposed adult-onset cases were in fact sufferers all along - just that their symptoms started off as too minor to notice.
"The data sets just aren't there to establish anything," he says.
"I'm suspecting that teenagers may not report symptoms because they are so mild, and it's not until they get to a certain level that they are any the wiser - but we just don't know."
It will, of course, be of little comfort to those currently plagued by itchy eyeballs and streaming noses. But the subject is surely a doctoral thesis waiting to happen.
Below is a selection of your comments.
My Mother was diagnosed with hay fever in her 70s. Eventually she went to the doctor as it was so bad and he said "Don't worry, you'll grow out of it". She did, in her late 80s.
Peter, Cropthorne, Worcs
I suddenly developed hay-fever when I was around 20. I remember the day, I was lying on the grass and suddenly started sneezing. It progressively became a problem very much relieved by the steriodal nasal sprays when they were introduced and I used them regularly. Now, at 71 I find my hay fever has suddenly more or less disappeared and I have not used any medication for the first time this year.
Margaret Dangoor, Richmond upon Thames
Up to the age of 59, having worked on many farms and in dust-creating factories, I never suffered from hay fever. I then spent two years abroad in various countries & temperatures - and still did not suffer. However, within days of returning to the UK, I've come down with it. I am convinced the problems we are now facing - which we conveniently call hay fever - is in fact pollution.
Tez, Derby, UK
I first developed hay fever symptoms over the summer, just after I left school at 16, when I happened to be working in a garden centre - personally, I'm inclined to think it was over-exposure to pollen that brought it on, and it's then got more severe every year that's followed. I have heard of a correlation between hay fever, eczema, and asthma, so it's probably also worth noting that I was a childhood eczema sufferer. It cleared up when I hit puberty, then re-appeared during the summer I first had hay fever and has only just cleared up again (seven years later).
Laura Davis, Farnborough, Hants, UK
I suffered from asthma as a child, gradually getting milder, never hay fever. But at 30, I suddenly developed it. I grew up around farms in the country and animals my entire childhood so I'm not sure the farm theory stacks up.
Rhona, Reading, UK
Ironically, I've gone the other way. I developed hay fever in my teens and suffered with it into my late thirties/ early forties. But since moving from south London to Lincolnshire 23 years ago it's gradually subsided to an occasional sneeze. No more sore eyes, blocked nose or headaches, and it's been like that most of the time I've been in Lincolnshire. Can you explain that one?
Brian Jones, Raithby by Spilsby, Lincs UK
Like most things in life I believe you can not put it down to a single reason. The body is an extremely complex machine and so are our lives. It could be that as an adult, a large amount of people get involved in gardening more, so spending more time cutting plants and breathing in pollen. On another idea, kids can be a lot less babyish when they have congested or runny noses. I'm guilty of suffering from man flu. Whereas my three-year-old will have the same level of cold and is perfectly happy to go to nursery, run around the house and be just as lively. So maybe some kids just get on with it when suffering from mild hay fever. Whereas an adult, the same person, later in life will feel worse or try to do something about it; like taking pills to relieve the symptoms. Does air conditioning effect us in any way? Bet most people didn't work in a air conditioned office 20-30 years ago. It's something that has changed over the last few years. Also more cars, more pollution. These might be factors to the whole issue, they might not.
Kevan Thurstans, Ewell
I had a terrible few years, losing several of my closest relatives, my job and moving home all at once. After that I suddenly developed a range of bad allergies including hay fever and wheat intolerance. I blame the high stress levels.
I developed hay fever when I gave up smoking, in my late 50s. Could the smoking have masked or stopped the allergy?
Terry Thompson, Uxbridge, Middlesex, UK