These items can hold heat and cause an adverse reaction. She advises riders to tack up the horse first, then apply the insecticide. When using sprays, protect the saddle with a sheet. Use a dab-on product to get in the small, exposed areas around the bridle. Before applying the insecticide, read label instructions carefully for frequency and amount of application.
Some products say to apply a 'fine mist,' which is less than wetting the hair.
The biggest thing for either is the skin should not be soaked. Overdosing the horse could cause a severe local skin reaction. They act like they're burning, which they are. Horses that are sensitive to a repellent will respond similarly. Should the horse have a reaction, hose the repellent off as soon as possible.