Seasonal Allergies Are Getting Worse — New Studies Show Why, And What To Do About It

HAMBURG — Some people sneeze constantly, others suffer from burning eyes, while some get itchy skin. Hay fever can show up in many forms, but the cause is always the same: the immune system overreacts to normally harmless substances like birch or grass pollen. These pollens circulate through the air in spring and summer, landing on the mucous membranes in the nose or eyes, where they trigger inflammation in allergy sufferers.

This allergic inflammation is always set off by a process called sensitization. That means the immune system, having previously encountered the pollen, wrongly flagged it as dangerous and produced custom antibodies in response. These antibodies attach themselves to immune cells called mast cells, which are packed with inflammatory agents like histamine. As soon as the antibodies bind to the pollen, the mast cells release those agents into the surrounding tissue – and the allergic symptoms kick in. This process happens within seconds or minutes, which is why doctors refer to it as an immediate allergy.

What’s surprising is that once the immune system has produced the relevant antibodies, years — even decades — can pass before someone actually starts experiencing hay fever. “It’s like a switch flips overnight,” says Ludger Klimek, head of the Center for Allergology in Wiesbaden. But researchers still don’t know exactly what triggers that switch.

Why are some people more susceptible?

There isn’t a single reason people develop allergies like hay fever. Still, researchers have identified a whole range of factors that influence a person’s risk.

One of those factors is genetics. “If both parents have allergies, two out of three of their children also have a high risk of developing an allergy,” says allergist Thomas Fuchs. If only one parent has allergies, the risk drops to one in three. But it’s not just genes — environmental factors matter too: People exposed to air pollution like exhaust fumes, and children with smoking parents, face a higher allergy risk. Gender, however, doesn’t seem to play a role: Overall, women are not significantly more affected by pollen allergies than men.

Children’s immune systems need to encounter a range of microbes.

In addition to risk factors, researchers have also found some factors that can protect against. Being exclusively breastfed for the first four to six months helps reduce allergy risk. And children who grow up around dogs or on farms are less likely to suffer from hay fever later in life. That’s likely because their immune systems are exposed to a wider variety of microbes early on. This ties into the so-called hygiene hypothesis. It suggests children’s immune systems need to encounter a range of microbes to learn how to tell friend from foe.

Scientists are now fairly confident that moderate exposure to germs is actually beneficial for the immune system’s development. So letting kids play in the mud might not be such a bad thing. It’s about striking the right balance, says Ludger Klimek. “Hygiene is important to keep out harmful pathogens, but a germ-free environment doesn’t help.”

The age symptoms start

Hay fever can strike at any age. Around 12 million adults in Germany say they suffer from pollen allergies, or about 15% of the population. Those aged between 18 and 49 report the highest rates.

But only just under 5 million people have received a formal diagnosis of hay fever from a doctor, according to health insurance billing data from 2019. Most of those diagnosed are in their teens or early adulthood. Among women, however, hay fever is more often diagnosed later in life, typically between 40 and 50.

Usually, the symptoms are severe enough to push people, especially when they’re young, to see a doctor. But in recent years, there’s been a noticeable shift: The average age at diagnosis has been rising. “We’re now seeing more cases of hay fever in people in their 70s and 80s,” says allergy expert Torsten Zuberbier from Berlin’s Charité hospital.

One reason might be the growing number of new pollen types spreading across Germany, including those from invasive plants like ragweed. These pollens are just as unfamiliar to older immune systems as they are to younger ones — and can still cause allergic reactions.

Are city dwellers more at risk?

People in cities are statistically more likely to suffer from hay fever than those in rural areas. One major reason is poor air quality near busy roads.

Exhaust fumes and airborne pollen interact, causing chemical changes to the pollen’s surface proteins. When these altered pollens land on mucous membranes, they provoke a stronger immune response, as studies have shown. In short, pollution makes the pollen more aggressive. And it lingers longer in the air. On top of that, pollutants irritate the airways and weaken the mucous membrane barrier.

Too often, urban planners choose fast-growing, inexpensive trees.

There’s also another issue that cities could fix: “Too often, urban planners choose fast-growing, inexpensive trees,” Fuchs says. Birch is a prime example, and it’s one many people are highly allergic to. Life in the city would be easier for allergy sufferers if less allergenic trees like poplars, lindens or oaks were planted instead.

According to data from the Robert Koch Institute, around 30 million people in Germany have some form of allergy, and roughly one in seven suffers from hay fever. Across Western industrialized countries, allergic diseases have been on the rise since the 1970s and remain at high levels. The number of allergy sufferers may still grow, with environmental pollution and climate change driving risk factors.

Plants affected by climate change now produce more, and more potent, pollen to survive. Researchers call this “climate stress.” At the same time, warmer temperatures are causing new plants, and therefore new pollens, to spread locally, and earlier springs mean longer pollen seasons. And when this stronger pollen mixes with pollution particles, the chances of triggering an allergy only increase.

Which medications work best?

There’s good news for allergy sufferers: No one needs to put up with a runny nose and watery eyes anymore. Today, there are highly effective medications that relieve hay fever symptoms.

Experienced sufferers usually know when their pollen season begins.

The simplest and most effective option is nasal sprays that combine cortisone and antihistamines. A similar effect can be achieved by using a cortisone spray along with an antihistamine tablet. Cortisone in nasal sprays comes with hardly any side effects because it doesn’t enter the bloodstream. Modern antihistamines also have no known long-term side effects, Zuberbier says.

Current treatment guidelines recommend taking these medications regularly, starting from when your specific allergen starts to circulate. Experienced sufferers usually know when their pollen season begins. Those who don’t can use a pollen forecast app.

Is hyposensitization useful?

The aim of hyposensitization is to teach the immune system something it should have learned in childhood: How to tell harmless from harmful substances. This “learning” happens in reverse during treatment. The immune system is slowly exposed to an allergen it wrongly reacts to, in a safe way. Over time (often over several years) doctors inject tiny amounts of the allergen under the skin, or patients take it orally through tablets or drops.

“The key is that the immune system encounters the substance through a different route than breathing. That way, it doesn’t get a danger signal,” Zuberbier says. The immune system learns the substance is harmless and builds tolerance. The big benefit: the treatment tackles the root cause, not just the symptoms. That’s important because hay fever sufferers are three and a half times more likely to develop allergic asthma, a risk that can be partially avoided.

“The problem,” says Martin Wagenmann, head of the German Allergology Association (DGAKI), “is that many patients never finish the desensitization process.” Treatment typically lasts three years. In general, this method is recommended for people whose symptoms don’t improve enough with medication and allergen avoidance. Whether it’s suitable for you is something best discussed with an allergist, as not all allergens are approved for desensitization treatment.

What else helps? 

A crucial everyday tip for those with pollen allergies is to avoid allergen exposure as much as possible and keep your home free of pollen. That means changing clothes after coming in from outdoors — or at the very least before bed. Evening showers help, too. Keep worn clothes out of the bedroom, wash bedding frequently, dry it indoors and vacuum often. Today’s vacuum cleaners come with HEPA filters that can remove even the smallest pollen particles from the air.

Beware of heavy rainfall: It can trigger the rare phenomenon known as thunderstorm asthma

Ventilation should also be done properly: in rural areas, open windows in the evening; in cities, do it in the morning – those are the times with the least pollen in the air. Special pollen screens can also be fitted to windows.

After it rains, pollen levels drop dramatically, making it a good time to go for a walk. Just beware of heavy rainfall: It can trigger the rare phenomenon known as thunderstorm asthma, when allergenic materials are suddenly released into the air and irritate the respiratory tract. Fortunately, that rarely happens.