When checking the labels of commercial fly sprays you will find the most common active ingredients are pyrethrins and pyrethroids. Pyrethrins are chemicals extracted from some species of Chrysanthemums.They provide a quick knockdown of pests and are safe for use on animals. Piperonyl butoxide is a synergist that is added to increase effectiveness. Unfortunately pyrethrins are broken down by sunlight so any residual protection lasts for only a few hours. The pyrethroids resmethrin, permethrin and cypermethrin are synthetic forms of natural pyrethrins that are more stable so an application will protect for several days. Pyrethrins and pyrethroids control a wide range of of horse pests like flies, gnats, ticks and lice. Pyrethrins also have the advantage of a pleasant scent.
Commercial fly sprays will list the concentration of each active ingredient on the label, the higher the percentage of concentration the longer the protection they will give. Fly sprays will be broken down between ready to use which are convenient, and concentrates that must be diluted before application and will normally be more economical to use. Check the label to be sure that the pests you want to control are listed.
When applying, brush your horse thoroughly to remove dirt and dust. Apply sprays while lightly brushing against the lay of the hair. When applying to the horses face spray on a soft cloth and wipe on keeping the insecticide away from eyes and nose. Do not spray before tacking up. Heat and pressure in the saddle area can become irritating. If signs of sensitivity occur bathe your horse with a mild, non-insecticidal shampoo and thoroughly rinse. Talk with your veterinarian immediately if signs of sensitivity continue. Check the label directions for re-treatment intervals and age restrictions. You will need to re-apply after your horse is washed or exposed to heavy rain.Some commercially available sprays should not be used on foals under 3 months of age.
And remember the most important thing about using sprays, always read, understand and follow all directions