A topical veterinary composition comprising: (a) about 15% to about 20% w/v fipronil; (b) optionally an insect growth regulator active agent; (c) a crystallization inhibitor which is a film-forming polymer and a non-ionic surfactant, wherein the weight:weight ratio of the film-forming polymer to non-ionic surfactant is from about 3:1 to about 1:1; and wherein the film-forming polymer is selected from polyvinylpyrrolidones, copolymers of vinyl acetate and vinylpyrrolidone, and polyvinyl alcohols; (d) optionally, an organic co-solvent selected from the group consisting of methanol, ethanol and isopropanol; (e) an organic solvent which is acetone, acetonitrile, benzyl alcohol, diisobutyl adipate, diisopropyl adipate, glycerol formal, butyl diglycol, dipropylene glycol n-butyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, liquid polyoxyethylene glycols, propylene glycol monomethyl ether, propylene glycol monoethyl ether, dimethyl isosorbide, 2-pyrrolidone, N-methylpyrrolidone, diethylene glycol monoethyl ether, triacetin, butyl acetate, octyl acetate, propylene carbonate, butylene carbonate, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, or any combination thereof; (f) optionally, about 0.01% to about 2.0% of an antioxidant: wherein the organic solvent (e) is present in the overall composition in a proportion representing the compliment to 100% of the composition; and, wherein, when present, the w/w ratio of the organic co-solvent to organic solvent is between 1/15 and 1/2; and wherein composition results in none or minimal crystallization at the site of application over a time period over 0 to 24 hours after application to the animal. (a) about 15% to about 20% w/v fipronil; (b) optionally an insect growth regulator active agent; (c) a crystallization inhibitor which is a film-forming polymer and a non-ionic surfactant, wherein the weight:weight ratio of the film-forming polymer to non-ionic surfactant is from about 3:1 to about 1:1; and wherein the film-forming polymer is selected from polyvinylpyrrolidones, copolymers of vinyl acetate and vinylpyrrolidone, and polyvinyl alcohols; (d) optionally, an organic co-solvent selected from the group consisting of methanol, ethanol and isopropanol; (e) an organic solvent which is acetone, acetonitrile, benzyl alcohol, diisobutyl adipate, diisopropyl adipate, glycerol formal, butyl diglycol, dipropylene glycol n-butyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, liquid polyoxyethylene glycols, propylene glycol monomethyl ether, propylene glycol monoethyl ether, dimethyl isosorbide, 2-pyrrolidone, N-methylpyrrolidone, diethylene glycol monoethyl ether, triacetin, butyl acetate, octyl acetate, propylene carbonate, butylene carbonate, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, or any combination thereof; (f) optionally, about 0.01% to about 2.0% of an antioxidant: wherein the organic solvent (e) is present in the overall composition in a proportion representing the compliment to 100% of the composition; and, wherein, when present, the w/w ratio of the organic co-solvent to organic solvent is between 1/15 and 1/2; and wherein composition results in none or minimal crystallization at the site of application over a time period over 0 to 24 hours after application to the animal. wherein the organic solvent (e) is present in the overall composition in a proportion representing the compliment to 100% of the composition; and, wherein, when present, the w/w ratio of the organic co-solvent to organic solvent is between 1/15 and 1/2; and wherein composition results in none or minimal crystallization at the site of application over a time period over 0 to 24 hours after application to the animal.