It’s no fun fending off uninvited airborne guests at the family cookout, but bloodthirsty bugs are an inevitable part of summer. Mosquitoes aren’t just an annoyance; they can carry infectious diseases like West Nile and Zika viruses, so it’s important to know the best ways to keep them at bay. 

Sprays containing the chemical DEET—developed by the U.S. Army after World War II and made commercially available in 1957—have long been the go-to option for mosquito repellent. DEET sprays came under scrutiny after isolated reports of seizures; these were subsequently dismissed as involving “off label” applications such as ingesting DEET (it’s best not to drink bug juice). DEET can occasionally cause a rash or skin irritation; however, the U.S. Environmental Protection Agency (EPA) and Centers for Disease Control and Prevention have both deemed DEET sprays as generally safe and effective for both adults and kids as young as two months. DEET also breaks down quickly in the environment, posing minimal danger to wildlife. 

For outdoor lovers seeking a more natural bug repellent, one formula performs as well as DEET at stopping mosquitoes and even better at repelling ticks: products containing oil of lemon eucalyptus extract, which contains the naturally occurring compound para-menthane-3,8-diol (PMD), a byproduct of the leaves of Corymbia citriodora tree. In a study published in the Journal of Insect Science in 2015, researchers from New Mexico State University found that it deterred mosquitoes for up to six hours, unlike largely ineffective candles, bracelets and ultrasonic devices. 

The PMD compound differs from lemon-eucalyptus essential oil, so look specifically for repellents containing PMD, found at most outdoors sports stores and major retailers. Lemon-eucalyptus essential oil itself is also sometimes touted as a natural mosquito deterrent, but like other essential oils like clove or citronella, the limited protection it offers is short-lived, as their volatile compounds evaporate quickly. While DIY insect repellents made from essential oils smell wonderful and are easy to make, they can also irritate the skin at higher concentrations and in some cases, such as clove oil, be toxic to pets. Products containing essential oils are also not registered by the EPA, and therefore not tested for efficacy.

Products containing Picaridin, a chemical modeled on black pepper, also have proven to be as effective as DEET. Picaridin-based products are better at deterring mosquitoes from landing than DEET, and are less oily and strong-smelling. 

The percentage of DEET or Picaridin in a product determines how long it protects, with higher concentrations providing longer protection with fewer reapplications. Those benefits taper off at 30 percent DEET and 20 percent Picaridin. Covering up with long sleeves and spraying clothes, not just skin, with insect repellent will help keep skeeters at arm’s length and also help keep off ticks.