Allergies vary by location and time of year and it seems that more people are suffering from them than in the past.
Greater cleanliness, double glazing and AC can result in less
resistance overall whilst travelling (or living) in different locations exposes people to different pollens.
There is also a theory that resistance diminishes with age.
RNSA (Réseau National de Surveillance Aérobiologique) carry out research into allergies in France and provide information by allergy causing agent, location and time of year.
Sufferers can register online for personalised email reports here : http://www.pollens.fr/bulletin-alerte/bulletin-alerte.php or use the panel below. The widget can be configured for 3 departments and 3 different pollens.