Background: Parietaria pollen is considered as one of the most common causes of allergic respiratory symptoms in the Mediterranean area but its presence is limited in the Atlantic area. Some leading patients from Muros, a small town on the Spanish Atlantic coast, complaining of nearly all year round respiratory symptoms happened to be allergic to Parietaria pollen.
Aim of the study: To evaluate the prevalence of Parietaria sensitization among patients from this Atlantic town, and its correlation with aerobiological data (concentration of Urticaceae pollen).
Patients and methods: Eighty-nine patients suffering from rhinoconjunctivitis and/or asthma from the area of Muros between January 1998 and January 1999 were included. Skin prick tests and serum-specific IgE (CAP Pharmacia) to Parietaria judaica and a battery of perennial or seasonal allergens were performed. Information about the seasonal and hourly rhythm of symptoms was obtained in each patient sensitized to Parietaria pollen. Atmospheric pollen was collected, using a Hirst-type volumetric pollen sampler, during 1998.
Results: Parietaria allergy was detected in 22 patients (25%) and represented the second most important aeroallergen after mites and along with grass pollen. The total atmospheric pollen recorded in Muros during the study period was 27,515 pollen grains, Urticaceae being the most important one (18,554 grains, 67% of the total). The proportion of Urticaceae pollen found in Muros was the highest among all samplers belonging to the Spanish Aerobiology Network. Maximum values of Urticaceae pollen were recorded during May and June. Intradiurnal variation of pollen counts showed maximum values between 11 a.m. and 1 p.m. A parallelism was observed between the rate of symptomatic patients and Parietaria type grain pollen count.
Conclusion: The prevalence of Parietaria pollen sensitization seems to be very important in this Atlantic area. The presence of very high levels of this pollen in its atmosphere explains this fact. Such sensitization should be taken into account concerning specific diagnostic tests.