Diphenhydramine and Sweating

In 2012, it was estimated that nearly 1 in 4 Canadians suffer from allergic rhinitis. To add, 78% of individuals working in predisposing environments are predicted to develop occupational rhinitis. Currently, the most popular treatment for rhinitis is antihistamine medication such as diphenhydramine, a first-generation antihistamine sold commercially as Benadryl®. Due it its anticholinergic effects, diphenhydramine has been suggested to impair the whole body sweating response during heat stress, potentially leaving consumers at an increased risk of heat-related illness. This randomized control trial approved by Health Canada will investigate whether ingesting extra strength diphenhydramine (50mg) will alter whole-body sweat losses during 60 minutes of exercise.