People allergic to winter pollens (such as cypress, ash and hazel) have not experienced major symptoms this season, since with the winter cold, plants have not started to release prominent amounts of pollen until early March. This delay has allowed trees (and particularly cypresses) to accumulate large amounts of pollen, which might now be released suddenly with peaks of very high concentration, and this may cause people who have never suffered from allergies to develop them now.

The pollinations that usually herald the arrival of spring (such as shade banana and parietaria, both highly allergenic) are being delayed as a result of the recent episode of low temperatures. Between next week and the last week of March these trees will begin to release pollen in notable quantities.

Weather models indicate that spring will be slightly warmer than usual and that it will rain in April.

With this information, the forecast of pollen and spore levels in the atmosphere in Catalonia for the coming months carried out by the Aerobiological Network of Catalonia (XAC) of ICTA-UAB and the Department of Animal Biology, Plant Biology and Ecology of the UAB (BABVE), led by researcher Jordina Belmonte, is as follows:

  • In early 2023, winter pollinations of cypress, hazel, ash and alder have been very low and at historic lows since 1994, delaying the onset of the allergy risk period until recently. Cypress pollination is expected to extend well into April.
  • During 2023, spring pollinations (poplar, banana, pine, parietaria, willow, maple, mulberry, grasses and, later on, birch, white goosefoot, plantain, plantain and olive) will follow the trend of starting somewhat late, but strongly, and could have a shorter duration than usual.

These predictions could change if the following occurs:

  • Episodes of rainfall, which, if heavy and during daylight hours, would wash pollen to the ground (this could happen with cypress and plantain) and, if less frequent, would provide water for plants set to bloom soon, particularly grasses, and could increase pollination and extend the period of presence in the air mainly of parietaria, grasses, white goosefoot, plantain and artemisia.
  • Temperatures are not as high as expected, which would make it possible to lengthen the pollination of plants (particularly herbaceous plants).
  • Episodes of very strong wind from directions without pollen or with little pollen (for example, from sea to land), which could reduce concentrations and modify the composition of the pollen spectrum.

According to the XAC, the most abundant allergenic pollen types in general in the atmosphere of Catalonia are cupressaceae (20.8%), shade banana (9.7%), oleaceae (olive, ash and privet) (8.6%), parietaria (5.3%), grasses (4.3%) and white goosefoot (2.4%), with significant variations in quantity depending on the geographical and climatic zones of Catalonia. The spores of the alternaria fungus, despite their significance in allergy, are not among the most abundant in the air (between 1 and 2% of the total number of spores).

The XAC has carried out a study of the trends of the total annual amount of seven main types of pollen and one fungal spore, measured in the 9 study localities since 1994. Considering decreasing trends as good and increasing trends as bad, they have obtained the following data:

  • The locality where more types of pollens are decreasing is Manresa and the one with the highest number of increasing pollens is Lleida. Among them, cited from more decreases to more increases, are Bellaterra, Tarragona, Girona, Vielha, Barcelona, Planes de Son and Tortosa.
  • Tree pollens (cypress, plane tree and olive tree) show a tendency to increase rather than decrease, particularly in the case of plane and olive.
  • Grass pollens (parietaria, grasses, white goosefoot and artemisia) show mostly decreasing trends, especially artemisia and grasses, followed by parietaria. Hemp pollen shows the most increasing trends.
  • The alternaria fungus shows mostly increasing trends, with results similar to those of the trees.

Real-time pollen levels

The XAC, within the framework of an agreement with Qualitas 4 Health and Swisens, collaborates in the development of an automatic observation model for pollen and other aerosols in real-time using artificial intelligence at the UAB campus (Cerdanyola del Vallès).

The SwisensPoleno Mars device on loan by the company Qualitas 4 Health was installed on the UAB campus, next to the traditional Hirst sensor, and is being trained since May 2021 to recognize the pollens in our area. The manufacturing company Swisens is collaborating in the generation of the algorithms needed to convert the recorded holograms into pollen types. For more information please visit

"It has turned out to be a much more complex challenge than we expected, and we are advancing slowly, but we began to publish on the XAC website real-time readings of one of the abundant and allergenic pollen types, cypress (cupressaceae in general)", says researcher Jordina Belmonte, who stresses that "the future lies in achieving real-time reporting of what is in the air and having enough equipment at an affordable price to cover the region representatively. It will be a great step forward to improve the quality of life of people with allergies, as well as for the diagnosis, treatment and prevention of respiratory allergies".

Jordina Belmonte also highlights the funding difficulties encountered by the XAC and the importance of finding enough new support to carry forward this important service for the community. "The XAC should be part of the services guaranteed by the government to its population, as happens in some autonomous communities in Spain and other countries." "We are very grateful, and I ask users to also be thankful for the companies and institutions that make the XAC possible."

Respiratory allergy and other related allergic diseases

Doctor Lorena Soto, allergist at the Hospital de la Santa Creu i Sant Pau and coordinator of the Respiratory Allergy Committee of the SCAIC, stresses the importance of asthma and allergic rhinitis, both in children and adults. These chronic diseases of the respiratory tract in springtime complicate the health of both the already known allergic population and those who begin to experience symptoms compatible with allergies. Primary care physicians are essential to help properly identify allergy sufferers and refer them to the allergy specialist for an accurate diagnosis and personalised treatment at all levels. She emphasizes the need for early detection, given the relationship with other associated allergic diseases in one same person, such as atopic dermatitis and food allergy.

Increased prevalence of respiratory allergy associated with weather changes and pollution

In Catalonia, a total of 2.5 million people suffer from allergic diseases, and this figure is expected to double by 2050. Abnormal weather conditions have increased the cases and complications of respiratory allergy sufferers, which has increased consultations to primary care and hospital emergency departments, with an increase in referrals to allergology services and the consequent impact on waiting lists.

The SCAIC estimates that 25% of the population suffers from allergic rhinitis and/or conjunctivitis and up to 12% from allergic asthma, which has an impact on health, social and family costs.

The most prevalent sensitizations in allergic patients are to grass pollen (51.6%), shade banana (38.7%), olive tree (35.5%), cupressaceae (22.6%), white goosefoot (6.5%), parietaria (10%) and alternaria (17%).

Prevalence is higher in cities and in areas with high levels of pollution. Pollution has a direct effect on respiratory allergic disease, not only because of the damage caused by toxic particles on the respiratory tract, but also because pollen alters its structure as a defense mechanism against pollution. This increases its ability to induce a nasal and/or bronchial inflammatory response and results in more symptoms and more severe respiratory allergic crises.

The Aerobiological Network of Catalonia (XAC): measurement of atmospheric pollens and fungal spores. Now also in real time.

On the XAC website (, on Instagram (@punt_informacio_aerobiologica) and on Twitter (@aerobiologia), users will find a weekly bulletin published with the predictions of the levels of pollens and allergen spores expected for the coming days, as well as graphs showing the dynamics of pollens and spores throughout the year and in comparison with previous years, pollen calendars, allergenic plants and other information of interest on aerobiology. The forecast can also be consulted in some apps (El Tiempo, Farmacias Ecoceutics) and services developed by third parties (Bot Telegram, Alexa Skills, Ajuntament de Cassà, etc.).

All information concerning the different services can be found at data (currently under development) will be available from March 2023 at