Our aim was to assess if patients with mono-sensitization or polisensitization to more common pollens in our environment are different.

We selected 11459 patients who showed hypersensitivity to some pollen from a total of 17785. These patients had been referred to the Allergy Unit of the Fundación Hospital Alcorcón for the first time for allergic respiratory evaluation between 1998 and 2002. This is the reference hospital for the southwest area of Madrid, which is made up of an urban area of 300.000 inhabitants and a rural area of 100.000 inhabitants.

Hypersensitivity to 2 or more pollens was observed in 9305 patients (81.2%). Monosensititation to grass was 9.1%, olea pollen 4.9%, platanus pollen 0.6%, Cuppressus arizonica pollen 1.1%, Artemisia pollen 1.4%, Amaranthus pollen 0.2%, Chenopod pollen 0.7%, Plantago pollen 0.6% and Parietaria pollen 0.1%. In the different logistic regression made for each pollen, age and/or to be female increased the probability to have mono-sensitization to the pollen tested. For instance: -Grass pollen: Age O.R.=0.98 (95% C.I. 0.98–0.99), Gender O.R 1.4 (95% C.I. 1.22–1.59). -Olea pollen: Age O.R=1.01 (95% C.I 1,003–1,015), Gender O.R.2.16 (95%C.I. 1.79–2.6). -Cuppressus arizonica pollen: Age and gender interaction O.R.=1.02 (95% C.I. 1.005–1.02). Rural or urban origin was not different between patients with mono or polisensitization to pollens.

Monosensitization to pollens is a rare phenomena in patients sensitised to pollens. Age and gender have a weak influence in determining the presence of mono or polisensitization to pollens.