Hay fever – the role of the immune system

Hay fever - the role of the immune system

Many suffer from hay fever. Despite its name, the disease has little to do with hay: it is not the dried grass that triggers the symptoms, but the pollen of freshly blossoming trees, grasses or herbs. There is hardly any pollen left in the hay. In the last twenty years, allergic diseases have increased significantly, especially in the rich countries of the northern hemisphere. Today, allergies are among the most common chronic diseases in regions with a “Western” lifestyle.

More and more allergies

The predisposition to allergic reactions is inherited. It can be found in around 30 per cent of adults and at least 35 per cent of school children in Switzerland. Our “hygienic” lifestyle and the usual carpeted, heated and double-glazed windows in our homes, which often contain an increased concentration of irritants, are responsible for the increase in hay fever and asthma.

Another factor for the increased occurrence of allergies is the decreasing number of children. Our children are less and less likely to come into contact with pathogens. However, the frequent defence against such pathogens in early childhood ensures that our immune system is sufficiently trained. The defences of our toddlers are increasingly “underemployed” and have time to come up with “stupid” thoughts.


Rural children are less at risk.

This theory is supported by a Swiss study that showed that six to fifteen-year-old farm children suffer from allergic diseases significantly less often than their peers. They are three times less likely to get hay fever than non-peasant children.

Daycare centres and crèches seem to have the same effect: the more children there are together, the higher the probability of infections, i.e. practical immune defence training at least would explain why children in former East Germany suffer less from allergies. Until recently, most children there were housed in crèches during the day.

Wind pollinators make you sick.

In the case of trees, grasses and herbs, the wind blows the male pollen away from the flowers and, luckily, to the female reproductive part of another plant of the same species. This process is called wind pollination and ensures that the ovum is fertilized. For the wind pollinators to have a chance to continue multiplying, they have to produce enormous amounts of pollen: rye has 21 million, sorrel even 400 million pollen per plant. In addition, pollen must be as light as possible so that the wind carries it well.

Pollen grains are, therefore, so small that they are practically invisible to the naked eye (8 to 100 thousandths of a millimetre). In addition, trees usually flower before the leaves unfold so that the leaves do not hinder pollination. We breathe in about a thousandth of a gram of pollen grains annually. This minimal amount is enough to plague more than a fifth of the population with hay fever. Of the approximately 3,500 plants in Switzerland, only around 20 are essential to allergy sufferers.


This is how hay fever begins.

Although the first signs of hay fever can appear in children as young as five or six, pollen allergy is a typical disease of school children. Sometimes, it doesn’t even only show up in puberty. Symptoms usually peak between the ages of 15 and 25. But older people are also increasingly suffering from hay fever. One must, therefore, also think of a pollen allergy in people over 70 with the corresponding symptoms.

Hay fever often begins with an annoying itching in the eyes, as if small grains of sand had gotten into them. The eye reacts with increased tear production, and the conjunctiva reddens and swells if the reaction is particularly severe. Eye rubbing increases redness and swelling. For some people, the eye symptoms are more complex than the runny, itchy nose. The nose bites and triggers a violent urge to sneeze. The cascades of sneezing attacks are typical of allergic rhinitis. They can be solid and, in severe cases, lead to exhaustion.

In contrast to a cold, the nose produces a lot of thin, clear secretion. Pollen allergy always occurs at the same time of year, especially when the weather is nice. Patients feel much better when it rains. Unfortunately, much pollen often flies through the air after the rain. The whole thing starts all over again. In many patients, hay fever symptoms decrease over the years or even disappear altogether. However, they remain sensitive throughout their lives and can develop another allergy (to food, pets or latex) at anytime.


Hay fever patients often suffer from irritated or blocked airways for weeks to months. The inflamed nasal mucosa also reacts sensitively to other stimuli: dust, cigarette smoke or changes in temperature cause the nose to run again weeks after the hay fever has subsided.

In about a third of cases, hay fever turns into allergic asthma. This process is called a “change of floors” because the disease has moved from the upper to the lower airways. Therefore, this complication turns a harmless allergy into a potentially dangerous one, and I’m particularly feared. The floor change can often be prevented by timely and correct therapy for hay fever.


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