Hay Fever: the Role of the Immune System

Many people suffer from hay fever. Despite its name, however, the disease has little to do with hay: It is not the dried grass that triggers the symptoms, but the pollen of freshly blooming trees, grasses or herbs. Pollen is hardly found in hay. In the last twenty years, allergic diseases have increased sharply, especially in the rich countries of the northern hemisphere. Today, allergies are among the most common chronic diseases in regions with “Western” lifestyles.

More and more allergies

The predisposition to allergic reactions is inherited. It can be detected in about 30 percent of adults and at least 35 percent of schoolchildren in Switzerland. Responsible for the advance of hay fever and asthma is probably our “hygienic” lifestyle as well as our usual homes with carpeted floors, heaters and double-glazed windows, in whose interiors an increased concentration of irritants is often found. Another factor in the increased incidence of allergies: the decreasing number of children. Our children thus come into contact with pathogens less and less frequently. However, the frequent defense against such pathogens in early childhood ensures that our immune system is sufficiently trained. The defenses of our young children are increasingly “underemployed” and have time to get “silly” ideas.

Rural children less at risk

This theory is supported by a Swiss study that showed that six- to fifteen-year-old farm children are significantly less likely to suffer from allergic diseases than their peers. Their likelihood of contracting hay fever is three times lower than that of non-farm children. Daycare centers and nurseries seem to have the same effect: the more children are together, the higher the probability of infections, i.e. effective immune defense training. At any rate, this could explain why children in the former East Germany suffer less from allergies. There, until recently, a large proportion of children were still placed in daycare centers during the day.

Wind pollinators make people sick

In trees, grasses and herbs, the wind blows the male pollen away from the flowers and, with luck, to the female reproductive part of another plant of the same species. This process is called wind pollination and ensures fertilization of the egg. In order for wind pollinators to have any chance at all of reproducing, they have to produce enormous amounts of pollen: Rye produces 21 million, sorrel even 400 million pollen per plant. In addition, pollen must be as light as possible so that the wind can carry it easily. Pollen grains are therefore so small that they are practically invisible to the naked eye (8 to 100 thousandths of a millimeter). In addition, trees usually flower before the leaves unfold so that pollination is not hindered by the leaves. We breathe in about one thousandth of a gram of pollen grains per year. This minimal amount is enough to plague more than one fifth of the population with hay fever. Of the approximately 3500 plants found in Switzerland, only about 20 are of importance to allergy sufferers.

How hay fever begins

Although signs of hay fever may first appear in five- to six-year-old children, pollen allergy is a typical disease of schoolchildren. Sometimes it even becomes noticeable during puberty. The peak of symptoms is usually reached between the ages of 15 and 25. But also older people suffer increasingly from hay fever. One must think therefore also with over 70-Jährigen with appropriate symptoms of a Pollenallergie. Hay fever often begins with an annoying itch in the eyes, as if small grains of sand had gotten into them. The eye reacts with increased tear production, the conjunctivae redden, and if the reaction is particularly strong, they also swell. Eye rubbing increases the redness and swelling. For some people, the eye symptoms are harder to bear than the runny, itchy nose. The nose bites and triggers a violent sneeze. Cascades of sneezing attacks are typical of allergic rhinitis. They can be very severe and in severe cases can lead to exhaustion. Unlike a cold, the nose produces a lot of thin, clear secretions. Pollen allergy always occurs at the same time of year, especially in fine weather. Patients feel much better when it rains. Unfortunately, after the rain, there is often a particularly large amount of pollen flying through the air. The whole thing starts all over again.In many patients, hay fever symptoms become less severe or even disappear completely over the years. However, they remain sensitive throughout their lives and may develop another allergy (to food, pets, or latex) at any time.

Complications

Hay fever patients often suffer from irritated or blocked airways for weeks to months. The inflamed nasal mucosa is also sensitive to other stimuli: dust, cigarette smoke or temperature changes cause the nose to flow again for weeks after the hay fever has subsided. In about one third, hay fever turns into allergic asthma. This process is called a “floor change” because the disease has moved from the upper to the lower airways. This complication turns a harmless allergy into a potentially dangerous one and is therefore particularly feared. Timely and correct therapy of hay fever can often prevent the change of tiers.