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Home > The ABC of air > Pollen

What is pollen?

The pollen grain is the male reproductive element of plants. There are two main types of pollens:

  • pollens carried by animals, in particular insects, which are large in size, not highly allergenic and are associated above all with flowers, which are generally highly visible and scented;
  • pollens carried by the wind, which are highly allergenic.

A grain of pollen is microscopic.

Production by plants and transport of pollen grains are subject to climatic conditions – temperature, wind, rain, humidity, and so on. Dispersion of pollen grains by the wind engenders major differences in concentrations depending on the species and the period of the year.


Over 20% of the French population suffers from respiratory allergy. The number of children who are allergic is steadily increasing. Numerous factors can be behind this phenomenon: interior environmental factors (dust mites, animal hair, etc.), exterior environmental factors (pollens, moulds, etc.) and/or atmospheric pollution factors (triangular relations between pollution, pollen and allergies). A pollen allergy is called pollinosis.

What are the manifestations of pollinosis? 

Very often benign, the symptoms can nonetheless be very severe, and even incapacitating (severe rhinitis with nasal irritation and itching, sneezing attacks, conjunctivitis and watering of the eyes, etc.) The most familiar form of pollinosis is “hay fever.” 


How can pollen allergy be limited?

A few simple pieces of advice during pollination periods:

  • Allergic individuals are encouraged to follow their treatment or ask their doctor’s advice.
  • Engage in outdoor activities early in the morning. At that time of day, the pollen rate is lower.
  • Avoiding opening the car windows. 
  • Limit walks in the country and prefer the seashore.
  • Avoid gardening, including mowing grass.
  • Rinse the hair in the evening to eliminate any pollen that has collected in it.
  • Remember to wear a hat and spectacles.
  • Avoid substances that produce additional irritation (tobacco, DIY and/or maintenance products, etc.)

Allergenic potential of pollens

At the initiative of the Réseau National de Surveillance Aérobiologique (RNSA – National Aerobiological Monitoring Network), in France pollen is classified by species according to an allergenic potential of between 0 and 5 (0 being zero potential and 5 very high potential). In our region, the most allergenic pollens are birch and graminaceous pollens, followed by hazel, alder, ash and oak.


Pollen de bouleau

graminée png

Pollen de graminée

Allergic risk

Each week, the RNSA determines the allergic risk as a function of the allergenic potential of the pollens encountered and their quantity. The allergic risk is classified between 0 (nonexistent) and 5 (very high). If it is high, the patient will need to follow his or her treatment correctly, and possibly strengthen it on the doctor’s advice. 

Interaction with atmospheric chemical pollution

Certain recent studies tend to show that atmospheric pollution increases the risk of  pollen allergy (or pollinosis). The growth in pollen concentrations is higher in urban environments, with an increase of 3% per year as opposed to 1% for rural areas. This difference is due to the higher rates of carbon dioxide (CO2) found in cities.

Evaluation of allergic risk in Normandy

In 2011, there were 62 pollen sensors distributed over the metropolitan territory. All data are centralised by the RNSA. In Normandy, two pollen sensors provide monitoring:

  • The first, located in Caen, has been managed by Air C.O.M. since 2003;
  • The second, installed in Rouen since 1988, is under the responsibility of Marie-Noëlle Amar of the APRIAN (Association Pour la Recherche et l’Information des Allergies en Normandie – Association for Allergy Research and Information in Normandy).

In parallel, the doctors who participate in the network (general practitioners, paediatricians, allergists, ENT specialists, etc.) monitor and keep account of symptoms (rhinitis, conjunctivitis, coughing, asthma, etc.) observed in the patients they receive each week. All these data are also sent to the RNSA.

capteur pollens

Capteur pollens