While flea and tick products can be an extremely valuable tool in keeping your dog free from these parasites, they also contain chemicals that can be harmful if not handled properly. Always follow the directions closely when using pest-killing products on your pet.
One common ingredient found in many flea and tick killers is pyrethroid, a pesticide linked to adverse reactions in pets. According to the EPA, more than half of all major pesticide reactions from pets stem from pyrethroid-based applications, while fewer than 6 percent come from non-pyrethroid medications. Two common pyrethroids are permethrin and etofenprox, and if you see either of those listed as an ingredient in your flea and tick killer, you should take extra care when dosing your pet.
The key to using a flea and tick killer or preventive safely is to follow the directions carefully. Weigh your pet before applying one of these products, because guessing wrong could lead to an accidental overdose. Never combine products, never use cat medications on dogs or vice versa, and don't mix doses -- don't assume that two doses for a 10- to 15-pound dog equal one dose for a 20- to 30-pound dog, for instance.