Toxicity to humans of frontline for dogs

Black dog image by Maksim Zinchenko from

Frontline is the trade name for a topical flea and tick agent that contains the prescription drug Fipronil. The solution is typically applied to the nape of a dog's neck, where it spreads and collects in the animal's hair and skin. Fipronil is also an ingredient in commercial pesticides. The drug is toxic to humans.

External Symptoms

One of the immediate symptoms of contact with Fipronil is irritation of the eyes or skin. Instructions for applying the solution caution users not to allow the drug to touch bare skin. You can easily rub the drug in your eyes if it is already on the skin of your hands, leading to irritation in both areas. Immediate washing is recommended.

Nausea and Vomiting

If ingested, Fipronil will cause nausea and vomiting. This reaction may be helpful in the long run, though unpleasant for the sufferer, as it removes some of the toxic agent from the system. Like the other symptoms of Fipronil poisoning, these abdominal symptoms could be related to some other catalyst. Seek medical attention if you are uncertain what is causing symptoms.

Minor Symptoms

Fipronil is a neurological agent that has a deadly effect on parasites. It interferes with the operation of the central nervous system, killing the pests. While it has more affinity for insect neurology, the drug can cause neurological symptoms in humans as well. While unpleasant, symptoms such as dizziness, sweating and drowsiness are not the worst that can happen. However, a sleepy feeling may cause a poisoned user to delay medical treatment.

Major Symptoms

More intense neurological effects of Fipronil poisoning include agitation, tremors and seizures. Agitation may be characterised by extreme emotional irritability and increased tension. Tremor is described as muscle spasms causing involuntary shaking of the body. It may be a precursor to full-on seizures, which are the strongest symptom of toxicity in humans.

Safety Precautions, Treatments and Outcomes

The label on every container of Frontline carries warnings and safety instructions for use of the product. Keeping the solution from contacting human hands or eyes is the top recommendation. If any Fipronil gets in the eyes, the label recommends flushing the eye with water. Immediate hand washing is recommended after each application, and each pipette should be wrapped in paper before being discarded. In cases where the solution has been ingested, you must seek medical attention immediately, and induce vomiting if medical help is more than 15 minutes away. Death from Fipronil poisoning is extremely rare. Patients tend to recover under medical treatment.