Most bug sprays protect you for somewhere between 2 and 8 hours, depending on the active ingredient and its concentration. A product with 20% DEET, for example, lasts roughly 4 to 5 hours, while higher concentrations can push protection closer to 8 or even 10 hours. But the number on the label is a best-case estimate. Real-world duration depends on what you’re doing, how much you’re sweating, and what’s biting.
DEET: The Most Common Active Ingredient
DEET has been the standard insect repellent since the 1950s, and it’s still the most widely available. It comes in concentrations from 4% to 100%, and the concentration controls how long protection lasts, not how strongly it repels insects. A 10% DEET product typically gives you about 2 hours of protection. A 25% to 30% product stretches that to around 5 to 8 hours.
What surprises most people is that going above 50% DEET doesn’t meaningfully extend protection time. Research shows little difference in duration between a 50% product and a 100% product. So a 30% spray handles a full evening outdoors, and anything higher is largely unnecessary for most situations. If you’re shopping and see concentrations like 98% or 100%, those exist mainly for extreme conditions, not because they last dramatically longer.
Picaridin: How It Compares
Picaridin (sometimes labeled as icaridin) is DEET’s main competitor and works against both mosquitoes and ticks. At 20% concentration, picaridin provides 8 to 14 hours of protection against mosquitoes, making it one of the longest-lasting options available. A 10% picaridin product lasts roughly 3.5 to 8 hours.
Picaridin has a practical advantage worth knowing about: it doesn’t damage plastics or synthetic fabrics the way DEET can. If you’ve ever noticed DEET dissolving the finish on a watch band or sunglasses frame, picaridin avoids that problem entirely. It also feels less greasy on skin, which is why it’s been gaining popularity in spray and lotion formulations.
Oil of Lemon Eucalyptus and Other Options
Oil of lemon eucalyptus (OLE) is the most effective plant-based repellent recognized by the EPA. At 30% concentration, it provides roughly 2 to 4 hours of protection. That’s shorter than DEET or picaridin at comparable concentrations, so you’ll need to reapply more often.
Products labeled as “natural” repellents, including those based on citronella, peppermint, or other essential oils, generally provide the shortest protection windows. Many last under 2 hours, and some wear off in as little as 20 to 30 minutes. If you’re spending extended time outdoors in mosquito-heavy areas, these won’t keep up without constant reapplication.
What Shortens Protection Time
The hours listed on a product label assume relatively calm conditions. In practice, several things eat into your protection window. Sweating is the biggest factor. Heavy perspiration dilutes and removes repellent from your skin faster than almost anything else. Water contact, whether from swimming, rain, or even wiping your face with a wet towel, has the same effect. Physical friction from clothing rubbing against treated skin also strips repellent away.
Heat and humidity accelerate evaporation of the active ingredient, which is unfortunate since those are exactly the conditions when mosquitoes are most aggressive. Wind can help keep mosquitoes away on its own, but it also speeds up how quickly repellent evaporates from exposed skin. If you’re hiking on a hot, humid day and sweating heavily, expect to get roughly half to two-thirds of the labeled protection time before you need to reapply.
When and How to Reapply
The simplest reapplication rule: if you start getting bitten, the repellent has worn off and it’s time to reapply. Don’t wait for a set number of hours if conditions are working against you. For a calm evening on a patio, a single application of 25% DEET or 20% picaridin will likely carry you through. For a full day of outdoor activity with sweating, plan on reapplying at least once.
If you’re using sunscreen alongside bug spray, apply the sunscreen first and give it about 10 minutes to absorb into your skin before putting on repellent. Reversing the order buries the repellent under sunscreen, reducing its effectiveness. Keep in mind that sunscreen typically needs reapplication every 2 hours, which is more frequent than most repellents require. When you reapply sunscreen, layer fresh repellent on top again.
Shelf Life of the Product Itself
Beyond how long bug spray works on your skin, many people searching this question want to know if the can from last summer is still good. DEET-based products are remarkably stable. They don’t have a strict expiration date in most cases and can remain effective for years when stored at room temperature away from direct sunlight. If the spray still smells normal and dispenses properly, it’s almost certainly fine to use.
Picaridin products are similarly stable. Natural repellents, however, tend to degrade faster because essential oils break down over time. If your citronella spray is more than a year or two old and has been stored in a hot garage, its already-limited effectiveness may be reduced further. Check for any expiration date printed on natural products and replace them more regularly than you would a DEET or picaridin spray.