Does Bug Spray Expire? It Depends on the Active Ingredient

Thanks for signing up! Access your favorite topics in a personalized feed while you're on the go. download the app Advertisement As the weather heats up, bugs start to come out. Our best defense against the itchy, painful bites is insect repellent. But some bug sprays will expire eventually. Here's what you need to know.

  • DEET-based bug sprays, such as Off, won't technically expire but may become less effective over time.
  • The same goes for bug sprays that use picaridin, oil of lemon eucalyptus, or para-menthane-3,8-diol.
  • But if the active ingredient in your bug spray is ethyl butyl acetylamino propionate, commonly known as IR3535, it may expire within 18 months.
  • This article was scientifically reviewed by Josh Bloom, who holds a doctorate in chemistry. He is now the director of chemical and pharmaceutical sciences at the American Council on Science and Health in New York.
  • Visit Insider's homepage for more stories.

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As the weather heats up, bugs start to come out. Our best defense against the itchy, painful bites is insect repellent. But some bug sprays will expire eventually. Here's what you need to know.

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How long bug sprays last

There is no one-size-fits-all answer here, but the consensus is that bug sprays have a shelf life of about three years. At that point, you should probably throw them out — not because they will harm you, but because they may be less effective in repelling bugs.

Whether a bug spray expires depends on the active ingredient, says Laurence Zwiebel, the Cornelius Vanderbilt chair in biological sciences at Vanderbilt University. Most active ingredients used in bug sprays are relatively stable and last a while. But even if the active ingredients don't expire, the overall formulation may become less effective over time.

Check the back of your bug-spray bottle to see which chemical it uses. Here's how long common active ingredients will last:

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DEET

The majority of popular bug-spray brands, such as Off, contain N,N-diethyltoluamide, more commonly referred to as DEET, as their active ingredient. DEET doesn't expire. This chemical is quite stable and has a long shelf life, Zwiebel says.

Picaridin

Picaridin is another chemical that is effective at repelling bugs. Like DEET, picaridin is a stable chemical. Picaridin-based repellents usually do not have expiration dates on the bottle. Brands that use picaridin include Sawyer and Ranger Ready.

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IR3535

IR3535 is a name commonly used for ethyl butyl acetylamino propionate. Bug repellents with IR3535 often do have expiration dates, since this chemical is less stable than DEET or picaridin. The expiration date might be as soon as 18 months from the manufacture date. Avon and Coleman are two brands that use IR3535 in their formula.

Oil of lemon eucalyptus or PMD

These similar oils are found in sprays like Repel and Off Botanicals. The synthesized version of OLE is called PMD, which stands for para-menthane-3,8-diol. Repellents with this active ingredient are stable for long periods and probably won't have an expiration date on the bottle. Repel is the most popular brand using OLE. You'll also find it in the Murphy's Naturals bug spray.

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How to tell whether your bug spray is bad

If you try out an old spray and notice that it smells funky or doesn't seem to be keeping bugs away from you, it's definitely time to buy a new bottle.

If you aren't sure how long you've had a bug spray or have questions about the formulation, it's best to call the company and ask about the specific product in question. The company will have the most up-to-date, formula-specific information for you.

Ashley Laderer

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