The number of adults and children suffering from plant allergies in the last few weeks has increased by between 20 and 30 per cent compared to last years figures. The estimate is based only on reported cases of allergies, which can cause asthma, conjunctivitis and breathing problems. According to the daily newspaper Corriere della Sera, the sudden change from cool to hot weather this year is responsible for the increased concentration of pollen in the air, the distribution of which would usually be spread out over the months of March and June. Among the plants causing problems are grasses, weeds, nettles, chestnut and olive trees.