Abstract: Objective To study the relationship between seasonal changes of the severity of psoriasis and aerobic floras on the tonsil surface in patients with psoriasis vulgaris.Methods The qualitative and quantitative analyses of aerobic floras of tonsil surface were conducted in psoriatic patients and health controls.Results The frequency of positive culture of some bacterial floras (Streptococcus pneumoniae, S. pyogenes and S. agalactiae) and their CFU/g were significantly higher in the patients than those in normal controls in the winter (P<0.05);but no significant differences were observed in the summer (P>0.05).Conclusion The above results suggest that microecological imbalance on the tonsil surface of the patients might be one of the causative factors in seasonal changes of the severity of psoriasis.

Key words: Psoriasis, Bacteria,aerobic