Frontline Plus is a popular flea treatment for dogs. It helps kill existing fleas and eggs as well as prevents new infestation. Frontline Plus is a topical treatment that requires monthly administration. It contains S-methoprene, an insect growth regulator that kills flea eggs and larvae, and fipronil, an insecticide that kills adult fleas. These chemicals effectively treat a flea infestation, but they can cause various side effects to your dog. Localized hair loss is one of them.
The most common side effect of using Frontline Plus is mild to severe skin irritation. You may notice redness and itchiness around the shoulder blade area where you administered the topical treatment. Hair loss or thinning hair is the second most common side effect of using Frontline Plus. Generally, this will occur right around the area where you administered the treatment. Over time, the hair will eventually grow back.