Earlier and earlier pollen allergies. In mid-January, six departments in the Grand Est region were on red alert. “The very mild start to the year 2023 favored the flowering of trees with in particular the first hazel pollen (Betulaceae family) which is already there and could come to interfere with allergies”, had indicated the National Aerobiological Surveillance Network (RNSA, in a press release published on its website on January 15.
In an interview with L’Express, Sophie Silcret-Grieu, allergist in Paris and member of the Asthma and Allergy association, explains how, with rising temperatures, more pollen – more allergenic – is released and how the simultaneous presence of pollution and pollen aggravates allergies.
L’Express: How long does pollen allergy season last?
Sophie Silcret-Grieu: It all depends on the pollen families. The tree pollen season is from February to April and May. The grass season runs from April to July. That of herbaceous takes place in the summer, sometimes until September. If we are unlucky, we can therefore be bothered by these allergies from February to September.
In 70% of cases, people are allergic to several things – we then say “polysensitised”. Some people may be allergic to a single tree, in which case the discomfort may last two or three weeks. But most people are often disturbed for months and suffer particularly between April and June, when the pollen peaks.
What are the impacts of global warming on allergies?
The phenomenon is complex. Global warming is one of the factors that explains the rise in allergies, but the reasons are multifactorial. What is indisputable is the explosion in the number of allergy sufferers in the world: we have gone from 5% 30 years ago to almost 30% today, and to 50% in 2050 according to WHO projections. . So it’s a real phenomenon. These diseases develop especially in the rich industrialized countries.
With global warming, the pollen season is extended over time, so the rise in temperatures lengthens the periods of allergy, which occur earlier (according to a study published in Nature, by 2100, this period could start up to 40 days earlier, end 19 days later and lead to a 40% increase in pollen production, Ed). Global warming will also modify the distribution of plant species and the allergenicity of plants, amplifying this allergenic power.
Plants with highly allergenic pollens go up towards the north of France…
Species hitherto confined to certain regions in the south are now developing further north due to climate change. This is particularly the case with ambrosia. In the 1970s, cypresses were planted in the south and birches in the north. These species favored high exposure to allergens. Birch is the most allergenic and pollinates in March and April. In the north of France, there are also alder and hazel, which pollinates from January (hazel only needs 5°C to flower and release its allergenic pollen, editor’s note). Ash can also cause allergies. The plane tree, which is more present in the south of France, can also cause allergies, but only if you are close to this tree.
It is normal for trees to pollinate at this time. But what is new is that it happens earlier than before and that the symptoms caused by these allergies are more and more violent. These symptoms of tree pollen allergies are increasingly accompanied by cross-food allergies.
How do these cross allergies work?
Once you are allergic to birch pollen, you risk developing cross allergies. There are common proteins in fruits and trees. When the body has made antibodies against certain proteins that make up birch pollen, if you find these proteins elsewhere such as in fruits, you can trigger allergic reactions by eating them.
These allergies only concern raw fruits. The most common come from stone fruits, pome fruits and nuts. The phenomenon of cross allergies also happens in people allergic to dust mites. There are also cross allergies to snails, whelks and shrimps for example, although they are less frequent.
These cross allergies are often not very severe: they cause tingling in the mouth, it itches and the lips can swell. But sometimes they lead to more severe forms such as generalized urticaria, edema, an asthma attack and anaphylactic shock. Cross allergies were once exceptional, but they have now become daily occurrences and allergists are overwhelmed. It has been observed that half of people allergic to birch pollen develop reactions to the fruit.
How does pollution affect allergies?
All pollutants have irritating effects on the respiratory tract. But irritated airways are much more permeable to pollen. In addition, some plant species make proteins to defend themselves against pollution, which themselves are sometimes very allergenic. The combination of pollution factors and the presence of pollen therefore considerably aggravates the symptoms of allergies. The interactions are multiple and produce both short-term and long-term effects. Acute exposure can lead to violent and immediate respiratory phenomena, while long-term exposure can lead to cancer and cardiovascular disease.
“The combination of pollution factors and the presence of pollen considerably aggravates the symptoms of allergies”
What are the medium or long term health risks due to recurrent allergies?
The long term effects are complications like asthma. This can go as far as respiratory failure with acute attacks favored by periods of allergy. While hay fever can only cause occasional sneezing, it can also progress to severe asthma attacks and hospitalizations. On the ENT routes, this time, these allergies can aggravate existing diseases such as nasal polyps. Nasal polyposis cannot be caused by allergy but it can maintain it or aggravate it. The allergological assessment is fundamental because it determines whether the allergic person is in a mild or severe form.
What are the practical tips to follow in order to reduce the health effects of allergies?
With the Covid-19 epidemic, we discovered that wearing a mask made people with allergies feel better. The mask can be particularly useful for people who wish to take a bike or motorbike ride in the fields, in the middle of the pollination period.
You can wash your face when you get home, wash and brush your hair. What matters is not to bring the pollens home. The worst pollution is indoor pollution, so you also need to ventilate your home. We caulked the houses in the 1970s, installed carpets… All of this creates a more favorable environment for dust mites.
Do not hesitate to consult the National Aerobiological Surveillance Network (RNSA) website and consult an allergist if you have respiratory symptoms, even if the appointment is in a long time. Our society has produced more allergy sufferers than allergists…