Suppression of seasonal allergic rhinitis symptoms with daily hydroxyzine.

The effectiveness of hydroxyzine in the suppression of allergic rhinitis symptoms was evaluated using a double-blind, parallel study design during the 1977 ragweed season. Forty-three subjects with positive ragweed skin tests and a history of an exacerbation of symptoms during August and September of the previous two years were randomly assigned to receive either hydroxyzine or placebo. Subjects scored the severity and duration of symptoms in a daily diary and adverse effects were evaluated from a structured interview at two-week intervals. Although drowsiness and dry mouth were frequent initially among the hydroxyzine-treated patients, these minor side effects rapidly disappeared as the dose was slowly increased, and all but one subject tolerated 150 mg/day. Subsequently, during the period of the highest ragweek pollen counts, the hydroxyzine-treated group spent significantly more days free of symptoms or with only mild sneezing, rhinorrhea, and eye symptoms than subjects who took placebo (p less than 0.05). Thus, hydroxyzine appeared to be well tolerated on a continuous daily basis and was effective in suppressing most of the symptoms of seasonal allergic rhinitis. Comparison of hydroxyzine with antihistamines more traditionally used for allergic rhinitis appears warranted.