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Your source for personal toxicology information.
The “Ask A Toxicologist” program is part of a growing effort by the College to improve public awareness and education regarding the toxicity of medication interactions, occupational chemicals, new drugs of abuse, venoms and plant toxins. The goal of the program is to provide rational, evidence-based answers to common medical toxicology questions – clearly and concisely. Members of the public are encouraged to submit questions through  for review by a panel of experts in human poisoning, who will post a consensus opinion written by one expert in the field. There is no charge for this service.
These answers are provided by volunteer medical toxicologists for the purpose of public education, and do not necessarily represent the policies or positions of the American College of Medical Toxicology.
Questions relating to an individual’s health concerns cannot be answered, as the program cannot create or replace a doctor-patient relationship. Additionally, we are unable to provide counsel, advice or interpretation for any legal issue. Questions and answers should be of a general nature, and of interest to a wide population. Not all questions will be able to be addressed.

Ask A Toxicologist

Is there any concern for human toxicity from household pet flea and tick products, such as fipronil (e.g. Frontline™)?

posted on 6:47 AM, September 23, 2015

Flea and tick infestations have long posed a problem for pet owners, leading to significant research into developing a highly effective insecticide that has low potential human toxicity. This led to the development of the broad spectrum insecticide fipronil. Fipronil is used for the control of fleas, ticks, ants, cockroaches and many other insects. Common sources for potential human exposure include spot pet preventive treatments, termite control products and insect bait products.

Despite widespread use, there are only a few reports of possible human toxicity from exposure to fipronil. Its wide margin of safety in humans is thought to be due to the fact that the target of fipronil is found only in insects and not in mammals. A seven-year review of exposures reported in 11 states showed that the majority of people exposed had mild temporary symptoms including headache, dizziness and tingling in the extremities. Other temporary symptoms reported after exposure included nausea, vomiting, fatigue, and skin irritation. Even with large exposures or intentional ingestions, the risk for toxicity appears to be low as supported by a published report of an accidental ingestion of ant bait with no development of any toxicity.

In summary, when used as directed on package labeling, the risk of human toxicity from exposure to fipronil in household pet flea and tick products is exceedingly low. Even with large exposures, effects are likely to be mild and temporary. To date, no long-term toxic effects have been reported in humans exposed to fipronil. 


  1. Lee, Soo-Jeong, Prakash Mulay, Brienne Diebolt-Brown, Michelle J. Lackovic, Louise N. Mehler, John Beckman, Justin Waltz, Joanne B. Prado, Yvette A. Mitchell, Sheila A. Higgins, Abby Schwartz, and Geoffrey M. Calvert. "Acute Illnesses Associated with Exposure to Fipronil—surveillance Data from 11 States in the United States, 2001–2007." Clinical Toxicology7 (2010): 737-44. Web.
  2. Fung*, Hin Tat, Kar Ki Chan, Wei Ming Ching, and Chak Wah Kam. "A Case of Accidental Ingestion of Ant Bait Containing Fipronil." Journal of Toxicology: Clinical Toxicology (2003): 245-48.
  3. "Fipronil." General Fact Sheet. National Pesticide Information Center, n.d. Web. 20 Sept. 2015.
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