July 12, 2011

Q. Can I use products with DEET to repel mosquitoes, ticks and other insects while I am pregnant?

A. The toxicity of the repellent DEET in large doses and the limited information available make it advisable for pregnant women to use only small amounts of this agent. They should avoid DEET type repellents on large areas of their bodies for long periods unless there is a strong reason, such as being in an area with a high risk of malaria, West Nile and/or Lyme disease.

Exposure to DEET can be limited by wearing long sleeved shirts and leg coverings to avoid biting insects and applying this agent only to exposed skin or clothing. Also use mosquito netting, screens on doors and windows and limit the time spent outdoors between dusk and dawn.

However, the repellent DEET (N,N-diethyl-3-methyl-benzamide, also known as N,N-diethyl-m-toluamide) is acknowledged as the most effective repellent. DEET has been used as a repellent for more than 50 years and is estimated to be applied several hundred million times yearly by North Americans alone. Scientific reviews have concluded that, when used as directed, DEET has an excellent safety record.

DEET can be sprayed on clothes, but can damage certain synthetic clothing such as spandex and rayon. Cotton and wool materials are not affected.

The higher the DEET concentration in the repellent formulation, the longer the duration of protection; this relation reaches a plateau at about 30% to 35%. Products with 10% DEET work for about 3 hours and products with 30% DEET work for 6 hours.

When there is a substantial risk of getting a disease from a mosquito or a large mosquito population, it is appropriate for pregnant women to use the concentration recommended for non-pregnant adults. Otherwise, when the purpose is primarily to avoid nuisance bites a lower concentration of DEET is advisable.

Answered by: Lisa Hupka, BSP

1. www.thomsonhc.com/micromedex2/ Reprotox ( Accessed on July 6, 2011 )
2. Insect Repellents. Canadian Pharmacist’s Letter; July 2010; Vol: 26
3. Christof Schaefer, Paul Peters, Richard K. Miller. Drugs During Pregnancy and Lactation 2nd ed. Elsevier BV; 2007, PG 458-9.
4. Prevention of arthropod and insect bites: Repellents and other measures. UpToDate. ( Accessed on July 6, 2011 )
5. www.cdc.gov/travel/ Travelers’ Health ( Accessed July 6, 2011)
6. The Merck Manual for Health Care Professionals. Malaria. ( Accessed July 6, 2011 )
7. Karen Jensen. Buzz Off - Helping patients select and properly use insect repellents. Pharmacy Practice. June 1, 2011