The present invention relates to the delivery of antihistamines through an inhalation route. Specifically, it relates to aerosols containing antihistamines that are used in inhalation therapy. In a method aspect of the present invention, an antihistamine is delivered to a patient through an inhalation route. The method comprises: a) heating a thin layer of an antihistamine, on a solid support, to form a vapor; and, b) passing air through the heated vapor to produce aerosol particles having less than 5% antihistamine drug degradation products. In a kit aspect of the present invention, a kit for delivering an antihistamine through an inhalation route is provided which comprises: a) a thin layer of an antihistamine drug and b) a device for dispensing said thin layer as a condensation aerosol.