Asthma is regarded as an inflammatory disease of the lung characterized by inflammatory mediator release, eosinophil recruitment, mucus hypersecretion and bronchoconstriction. The aim of the present study was to evaluate the protective effect of Urtica dioica seeds on allergic asthma. Mice were sensitized via intraperitoneal injection of ovalbumin (OVA) containing aluminum hydroxide on days 1 and 14. On days 24, 26, 28 and 30, the mice underwent challenge through inhalation of 1% OVA aerosolized using an ultrasonic nebulizer. Animals sensitized and challenged with OVA were treated with theophylline 1% while the other asthmatic group received 3.3g.kg⁻¹ nettle seed extract by gavage 15min after each challenge for eight consecutive days (days 23–30). At the end of this period, the mice were euthanized on day 31 for analysis of lung tissue, bronchoalveolar lavage fluid (BALF) and blood. The results showed that nettle seed significantly (P<0.05) decreased the following in lung tissue: percentage number of eosinophils in blood (1.4±0.3%) and BALF (22±5%); Th2 cytokines including IL-5, IL-13, and IL-33 (43.12±3.5, 63.76±3.3pg/ml, 10.40±0.81ng/ml respectively); mRNA expression of IL-4 (1.56±0.3), IL-5 (1.42±0.1), IL-13 (1.58±0.04) and Muc5 (1.83±0.2); inflammatory cell infiltration (perivascular inflammation: 1±0.3; peribronchial inflammation: 1.5±0.2); goblet-cell hyperplasia (1.5±0.2); and mucus hypersecretion (25±10%). The findings demonstrated a protective effect of nettle seed on OVA-induced allergic asthma in mice.