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vector-borne disease section

Mosquito Repellent

When mosquitoes bite, they can spread viruses (like West Nile virus and Zika virus) that can make people sick. The best way to prevent diseases spread by mosquitoes is to prevent mosquito bites. EPA-registered insect repellents work to prevent mosquito bites, and they are safe for use on pregnant and breastfeeding women and children.

When choosing a repellent to prevent mosquito bites, look for the following information on the product label: 

The active ingredient is usually listed on the front label of the repellent containerActive Ingredient

EPA-registered repellents will contain one of the following active ingredients:
  • DEET
  • Picaridin
  • IR3535
  • Oil of lemon eucalyptus (OLE)
  • Para-menthane-diol (PMD)

Mosquito Protection

The label will usually list "mosquitoes" as one of the insects that the product repels. The label might also list mosquito-borne diseases that the product will help prevent.
  • Example: "Long Lasting Protection From Mosquitoes, Ticks and Biting Flies"
  • Example: "Repels Mosquitoes That May Carry West Nile Virus"

Protection Time or Active Ingredient Percentage (%)

Not all products will list the number of hours that the repellent works to prevent mosquito bites. A repellent with a higher percentage of active ingredient will work longer to keep mosquitoes from biting you, but DEET products with more than 50% DEET will not usually provide extra protection against mosquito bites.

Choose a repellent that will protect you for the amount of time you plan to be outdoors. If you plan to be outside in your yard for a short time, a repellent with a low percentage of active ingredient (about 10%) will work well to prevent mosquito bites. However, if you plan to be outside in areas with mosquitoes for several hours, use a repellent with a higher percentage of active ingredient (20-30%) to protect you for a longer time. When you are sweating or getting wet, repellents don't last as long.

Who should use mosquito repellent and when?

You should use repellent when you spend time outdoors in areas with mosquitoes, especially during warmer months of the year when mosquitoes are most active and when you are more likely to be bitten.

Different kinds of mosquitoes are active at certain times of the day. For example, the Culex mosquitoes that spread West Nile virus bite most often at dawn and dusk. You should use repellent if you will be outside early in the morning or late in the evening before it gets dark. 

Older adults (over 60 years of age) are at greater risk of getting very sick from West Nile virus and should use mosquito repellent to prevent mosquito bites.

The Aedes mosquitoes that may carry Zika virus (called Aedes aegypti and Aedes albopictus) are found in some areas of California and bite most often during the day. At this time, the risk for Aedes mosquitoes spreading Zika, dengue, or chikungunya in California is low, but these diseases are found in other parts of the world. If you travel or if you live in areas of California with these Aedes mosquitoes, you should use repellent if you are outside during the day. For more information on Aedes mosquitoes, visit the CDPH Aedes Mosquitoes webpage.

The greatest risk from Zika is to a pregnant woman's developing baby. Pregnant women and women planning pregnancy should use mosquito repellent to prevent mosquito bites while traveling in areas where Zika could be spreading. Learn more on the CDC Zika Travel Information website


To protect children and babies from mosquito bites:

        • Dress children in clothing that covers arms and legs
        • Cover a child's crib, stroller, or baby carrier with a mosquito net
        • Use insect repellent according to label instructions
          • Do not use repellents with OLE or PMD on children younger than 3 years

Annual risk of mosquito bites and disease transmission in California click to enlarge (PDF)

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