Climate change and pollen: why allergies are on the increase

Allergies occur when the body’s immune system over-reacts to substances that are actually harmless such as pollen from flowers circulating in the air.

Typical symptoms of a pollen allergy are sneezing, a runny nose, an urge to cough and red, itching eyes. This is mostly referred to by the non-technical term hayfever. Doctors refer to it as “allergic rhinitis”. In Germany, about 15% of adults have hayfever.

Bronchial asthma, a chronic respiratory disease, can also be triggered by an allergic reaction to plant pollen. This is then referred to as allergic asthma. Unlike hayfever, the symptoms (mainly shortness of breath and wheezing) come in the form of sudden attacks.

The effects of climate change have been felt also in Germany for quite some time: they include a rise in the frequency of extreme weather events such as storms or summer heatwaves and the gradual rise in average temperatures. According to the German Meteorological Service DWD, the five hottest years since 1880 did not occur until very recently, but then ran consecutively from 2015 to 2019. Whilst many people are pleased about the long summers, others increasingly suffer from heat-related health problems – particularly cardiovascular disorders.

But how do these changes in the climate in Germany and Europe affect plants, how long they bloom and the spread of pollen? And what might the consequences be for people with pollen-related allergies?

Put simply, the increase in temperatures is also causing a change and shift in the seasons: autumn and winter are becoming milder in terms of their average temperatures. Spring and summer are becoming longer and hotter. Plants are starting to flower earlier and for longer.

Flowering periods are longer overall, increasing periods of high pollen count. Another factor is that species of plants not previously native to Germany are establishing themselves here as the temperatures rise. One of the main allergens (the plants that cause the pollen allergy) is common ragweed (Ambrosia artemisiifolia). This species of ragweed is particularly allergenic. It originated in North America and came to Europe as a result of the globalization in trade.

Another factor in the increased pollen count is believed to be the increase in carbon dioxide (CO₂) levels in the atmosphere since carbon dioxide can increase pollen production in many plants. If correct, that would mean that CO₂ emissions from households, industry and traffic are not only crucially responsible for global warming; they could also be partly responsible for the rise in pollen-related respiratory disease.

The increase in pollen count can exacerbate existing allergies and prolong the acute symptom phases.

Climate change boosts pollen count at a number of levels:

• Many plants are starting to produce pollen earlier.
• The pollen season is becoming longer.
• Many plants are increasing the amount of pollen they produce.
• Plant species, including those such as common ragwort which have a high allergy potential, are establishing themselves as native species.

In addition to the increase in pollen count, climate change has other consequences that could be increasing or exacerbating respiratory diseases:

• More frequent heatwaves and increased pollution due to higher temperatures: these make it more likely that people will get severe forms of chronic respiratory disease.
• Heavier rainfall with flooding: this increases air humidity and could exacerbate chronic respiratory disease.
• More frequent extreme weather events such as storms: there are indications that their abrupt effects on pollen count could also make asthma attacks more likely.

There are ways for people with pollen allergies to respond to an increase in the pollen count and mitigate symptoms:

• Outdoor activities should be avoided as far as possible when the airborne pollen count is particularly high.
• It is advisable to keep windows shut when the pollen count is high. It’s better to air rooms when the pollen count is low according to the pollen count forecast.
• The doctor treating the condition can prescribe drug treatment for the allergy and adjust it as required.
• Targeted immunotherapy (hyposensitization) can attenuate or even neutralize the allergic reaction under certain circumstances.

The German Pollen Information Service foundation (PID) provides a number of services that allow you to adjust your activities around the current pollen count. For example, the PID website provides daily and weekly forecasts of the pollen count.

Detailed information about the broad topic of allergies can be found on the allergieinformationsdienst.de website (in German).