Updated: Mar 14, 2022
Itchy bumps are a real bummer, and they're especially no fun on our little ones. Add the annoyance of scratching to the potential of scary mosquito-borne illnesses such as West Nile, Lyme Disease, Malaria, and Zika, and you get many parents searching for ways to keep bugs off of their families. The most effective way to repel insects is with bug spray containing the notorious ingredient DEET. But will spraying baby (or yourself) with DEET cause harm? Short answer: DEET has not been shown to be harmful to adults, children, or babies as long as usage recommendations are followed (provided below). In fact, a recent review on insect repellent states that "DEET has an excellent safety profile and remarkable protection against mosquitoes" (Nguyen et a., 2018).
This answer may come as a surprise to many people, as DEET has acquired a bad rap. This started in the 1980's with reports correlating DEET-containing insect repellent exposure with seizures and encephalopathy (damage to the brain) in children (Roland et al., 1985; Edwards and Johnson, 1987). However, DEET's bad reputation based on these reports is unwarranted. Studies in the intervening decades have shown that DEET is safe when used as recommended (i.e. on skin, not ingested), and that it's the most effective repellent against insects.
Let's dive into the safety data. The initial reports of DEET inducing brain dysfunction are certainly alarming; how do we know they aren't valid? First off, we have to pay attention to correlation vs. causation: are two events actually happening together because one thing causes the other? As seizure disorders occur in 3%–5% of children and an estimated 23%–29% of children are exposed to DEET, the few reported seizure cases overlapping with DEET exposure likely happened by chance (Koren et al., 2003). In fact, two large studies investigating over 29,000 DEET exposure cases reported to poison control revealed that "DEET presents little to no risk when applied according to product labels" (Swale and Bloomquist, 2019). Lethal dose studies actually place DEET in the same toxicity category as table salt (Swale DR, Bloomquist, 2019).
What about DEET exposure during pregnancy? The available data in both animals and humans are again reassuring. A study in rats and rabbits revealed no adverse effects when DEET was ingested, except for the highest dose of 325 mg/kg per day which by far exceeds recommended levels. This dosage led to maternal toxic effects and low birth weights of offspring, but even at this extreme dose there was no evidence of toxic effects or malformations in the offspring (Koren et al., 2003). In humans, a randomized study of 900 pregnant women and their children demonstrated that even with daily topical application, no adverse survival or growth effects were observed at birth and at 1 year of age (Koren et al., 2003).
While we aren't entirely sure how DEET works, the main theory is that it disrupts a mosquito's ability to locate humans by blocking antennae receptors. DEET's effectiveness is directly related to the concentration applied, with higher levels effective for longer time periods. The max recommended concentration of DEET is 30%, which provides 6 hours of protection. Other commercially available repellents contain 15%, 10%, or 5% DEET, which protects for 5, 3, or 2 hours, respectively (Koren et al., 2003).
The recommendations for DEET application by age are as follows (based on Sorge, 2009 and AAP guidelines):
Infants younger than 2 months: don't use DEET products. If necessary, use mosquito netting with an elastic edge to fit tightly around a stroller.
Babies age 2 months to 1 year: only apply repellent once daily.
Children age 1 to 12 years: 2 applications may be safely used daily.
12 years old through adulthood: don't exceed 3 applications daily.
Choose DEET concentration based on desired protection time, keeping in mind that 30% is the highest amount recommended for both children and adults. To limit the amount of DEET that reaches the bloodstream, don't spray directly on the face (apply with hands), never use over cuts or irritated skin, don't apply to skin under clothes, and wash hands after application to limit ingestion. Avoid sunscreen/bug spray combo products, as sunscreen should be applied more frequently. If you are also using sunscreen, apply sunscreen first and insect repellent second.
Nguyen QD, Vu MN, Hebert AA. Insect Repellents: An Updated Review for the Clinician. J Am Acad Dermatol. 2018 Nov 2:S0190-9622(18)32824-X.
Roland EH, Jan JE, Rigg JM. Toxic encephalopathy in a child after brief exposure to insect repellents. Can Med Assoc J. 1985 Jan 15;132(2):155-6. PMID: 3965068; PMCID: PMC1346745.
Edwards DL, Johnson CE. Insect-repellent-induced toxic encephalopathy in a child. Clin Pharm. 1987 Jun;6(6):496-8. PMID: 3690996.
Swale DR, Bloomquist JR. Is DEET a dangerous neurotoxicant? Pest Manag Sci. 2019 Aug;75(8):2068-2070.
Koren G, Matsui D, Bailey B. DEET-based insect repellents: safety implications for children and pregnant and lactating women. CMAJ. 2003 Aug 5;169(3):209-12.
Sorge F. Prevention with repellent in children. Arch Pediatr. 2009 Oct;16 Suppl 2:S115-22.
“Safe Use of Insect Repellents Can Minimize Itching, Scratching.” American Academy of Pediatrics, American Academy of Pediatrics, 1 June 2013, www.aappublications.org/content/34/6/16.2.