The clinical effects of second generation antihistamines on pruritus caused by various skin diseases were examined by keeping a daily record of their effects.Five mg of olopatadine hydrochloride (Allerock) was administered to the subjects twice daily. The severity of the pruritus and the scratch scars were scored before, and then 2 weeks and 4 weeks after, commencement of treatment. The severity of the pruritus during the day and night was measured by using a visual analogue scale (VAS), and a daily 'itch score' was recorded in an 'itch diary.'The itch scores for both day and night, as well as the scratching scores, the VAS values and the 'itch score,' significantly decreased after administration of olopatadine. The VAS value was significantly correlated with the itch scores and patient responses in the medical interview. Statistical analysis showed that there was a prompt alleviation of the pruritus in urticaria a day after administration, followed by asteatotic dermatitis and atopic dermatitis, in the order of improvement, within the next several days.The VAS value for pruritus was highly correlated with the itch score, showing that the VAS value was suitable for evaluating daily changes in the severity of pruritus. These results suggest that second generation antihistamines like olopatadine hydrochloride, which showed a prompt response to histamine, are effective against pruritus in urticaria, and that continuous use of these antihistamines is effective against pruritus in other forms of skin disease, such as asteatotic dermatitis and atopic dermatitis in which other chemical mediators besides histamine may be the triggers for pruritus.