When your nose runs and your eyes itch in spring, many people immediately think of birch or grass pollen. But in recent years, another plant has been causing increasing problems: Ambrosia artemisiifolia, also known as mugwort. This inconspicuous plant is a late bloomer that releases vast quantities of pollen into the air from July to October. The dangerous thing about it: Even tiny amounts are enough to trigger severe allergic reactions. Millions of people in Europe are now affected, and the number is rising.
What is ragweed actually?
Ragweed originates from North America and likely arrived in Europe in the 19th century via contaminated seeds and animal feed. Today, it is particularly widespread in France, Hungary, Italy, Austria, and Germany. The plant prefers to grow on roadsides, construction sites, or fallow land—anywhere where the soil is regularly disturbed.
Visually, it appears inconspicuous: green, deeply incised leaves, heavily branched stems, and a height of 30 to 150 centimeters. Only upon closer inspection do you notice the small, greenish inflorescences. While most allergenic plants bloom in spring, ragweed only begins blooming in midsummer and lasts into autumn.
The spread in Germany and Europe
The fact that ragweed has been able to gain a foothold in Europe so quickly is due not only to its high adaptability, but also to climate change. Longer warm periods and mild winters favor its spread. Transport via animal feed, seeds, or construction sites also contributes to this. Bavaria, Baden-Württemberg, Brandenburg, and Hesse are particularly badly affected, but populations are steadily increasing in other federal states as well.
One problem is the lack of awareness among many citizens. Those who don't recognize the plant don't remove it in time – and so it continues to spread.
Why ragweed is so dangerous
The greatest danger lies in its extreme allergenicity. Just five to ten pollen grains per cubic meter of air can trigger symptoms in sensitive people. By comparison, grasses need at least ten times that amount. Because ragweed blooms so late, it significantly prolongs the suffering of many allergy sufferers. Those who already suffer from hay fever in the spring are often plagued again in late summer. Some even develop an allergy for the first time, despite previously being symptom-free.
Particularly problematic is the high risk of allergic asthma. Ragweed pollen penetrates deep into the respiratory tract and can cause chronic inflammation. Studies show that those affected are significantly more likely to develop asthma than those with other pollen allergies.
Symptoms of a ragweed allergy
The symptoms are varied: a runny or stuffy nose, sneezing, red and itchy eyes, and breathing problems are among the most common. Some sufferers also report skin rashes, itching, or headaches. They often feel tired, fatigued, and less productive.
Another phenomenon is cross-allergies. People who are allergic to ragweed often also react to certain foods, such as celery, melons, cucumbers, or bananas. Even small amounts can then cause itching in the mouth or swelling.
Diagnosis by an allergist
Anyone who regularly suffers from these symptoms in late summer should definitely consult an allergist. A skin prick test or special blood tests can definitively diagnose a ragweed allergy. In some cases, a provocation test is also performed, in which the patient comes into contact with the allergen under controlled conditions.
A confirmed diagnosis is important in order to detect secondary diseases such as asthma at an early stage and to be able to treat them specifically.
Treatment options
Therapy is divided into two areas: short-term relief and long-term treatment of the cause.
For quick relief, antihistamine tablets are usually used to reduce itching, sneezing, and watery eyes. Nasal sprays containing cortisone work against inflamed mucous membranes, while eye drops relieve the burning sensation in the eyes. If the lower respiratory tract is involved, doctors also prescribe asthma medication.
The only causal treatment is desensitization. This involves exposing the body to increasing doses of the ragweed allergen over several years. The goal is to build tolerance and permanently reduce symptoms. Studies show that this method can be particularly successful in treating ragweed allergies.
Prevention in everyday life
Even if medication helps, your own behavior plays a major role. Allergy sufferers should use pollen calendars during the flowering season and limit outdoor activities, especially on dry, windy days. Anyone who has been outside should change their clothes and shower to remove pollen from their skin and hair. Pollen screens and regular vacuuming with a HEPA filter can help in living spaces. Walks are most pleasant after rain, as the air is then largely pollen-free.
But it's not just those affected who can take action. Anyone who discovers ragweed should remove the plant, including the roots, before it blooms – ideally wearing gloves and a face mask, as skin contact and inhaling the pollen can also cause irritation. Many German states have reporting centers where larger quantities can be reported.
Social and economic consequences
The health problems caused by ragweed also have economic consequences. As the number of allergy sufferers increases, so do the costs of medications, doctor visits, and treatments. Furthermore, severe symptoms lead to work absences and lower productivity.
Agriculture is also affected: Ambrosia can infest fields and reduce the yields of crops such as sunflowers, corn, and soybeans. Some countries, such as Hungary, have therefore already introduced legal regulations to combat ragweed.
Climate change as an amplifier
The fact that ragweed plays such a significant role today is also related to climate change. Longer growing seasons and higher CO₂ concentrations promote growth and pollen production. At the same time, the plant is spreading to regions that were previously too cool. Experts fear that the burden in Europe could double or even triple in the coming decades if no countermeasures are taken.
What needs to be done now
Combating ragweed is a community effort. Education is a key element: The more people recognize the plant, the easier it is to contain it. Municipalities and road maintenance departments should consistently remove known populations before they begin to flower. Europe-wide strategies are also necessary, because pollen knows no national borders. At the same time, more research is needed to develop new treatment approaches and effective monitoring systems.
Conclusion
Ragweed has long been more than just a harmless "weed." It is one of the most aggressive allergens in Europe and poses a growing challenge to healthcare systems. Its long flowering period, enormous pollen production, and close connection to climate change make it a problem that we can only tackle together.
The good news: Everyone can contribute—whether by removing individual plants from their own garden, reporting infestations, or consciously managing their own allergies. The sooner we act, the better we can contain the spread and reduce the burden on millions of people.
