Although DEET is no longer the only reliable way to fight mosquitoes, it's still a top choice when the insects seem relentless. In two separate professional tests, products with at least 15 percent DEET are among the top performers for repelling mosquitoes and ticks. In addition, several users on retail sites claim that DEET-based mosquito repellents are the only ones that work reliably for them. Health experts say DEET-based insect repellents are safe for adults and children over two months old, but you should still take some precautions to limit your exposure to the chemical, such as washing it off promptly after you come inside.
The mosquito repellant that does best in professional tests is Off! Deep Woods VIII (Est. $15 for two 6 oz. cans), an aerosol spray with 25 percent DEET. In one study published in the Journal of Insect Science, this spray did better than any other insect repellent at keeping mosquitoes at bay when it was first applied. Only 6 percent of the mosquitoes in the test chamber approached the hand sprayed with Off! Deep Woods VIII, while 61 percent were drawn to an untreated hand. However, after 4 hours, the product was much less effective, attracting nearly 30 percent of the available mosquitoes (compared to 68 percent for the untreated hand).
This product does even better in a test conducted by ConsumerReports.org – which, unlike most of the site's reviews, is free to view online. That test found that Off! Deep Woods VIII continued to repel two different species of mosquitoes for a full 8 hours, putting it on a par with the top performer in the test. However, it proved somewhat less effective at repelling deer ticks; its power petered out about 5 hours after application.
The roughly 100 reviews we found for Off! Deep Woods at Amazon.com and Drugstore.com are generally enthusiastic. Users say the product is very effective and easy to apply, and it doesn't have the greasy feel of many DEET-based products. Most users also say its odor isn't too bad, but some say it has an unpleasant chemical smell.
Repel 100 (Est. $9 for 4 oz.) provides even longer-lasting protection than Off! Deep Woods VIII. In the Journal of Insect Studies test, it got off to a less impressive start, attracting 10 percent of the mosquitoes in the test chamber. However, after 4 hours had passed, the percentage had barely budged, with only 14 percent of the mosquitoes approaching the treated hand.
However, Repel 100 contains far more DEET than any other insect repellent – a whopping 98.1 percent. If that seem like overkill, it might be as past expert testing has found that DEET concentrations higher than 30 percent did little to boost a product's effectiveness, but could increase the risk of serious side effects, such as rashes, disorientation, and seizures. Reviews at Amazon.com and Drugstore.com indicate that the high DEET levels in Repel 100 have other downsides as well. There are complaints that it eats through plastic. Several reviewers gripe that a bottle of Repel 100 leaked inside their suitcases and ruined everything inside even after being wrapped in an additional plastic bag. Many users also object to the product's oily feel and overpowering chemical smell, and some say it gave them a rash.
Be that as it may, user feedback is relatively strong -- 4.3 stars following more than 1,150 reviews at Amazon.com. The simple reason is that Repel 100 works. Users that hate the smell, feel, and what it can do to plastics often grant it 4 star and even 5 star ratings for its effectiveness -- even while strongly cautioning others to be prudent in using it.
If you want long-lasting protection without such high exposure to DEET, one option is 3M Ultrathon (Est. $9 for 2 oz.). This product is a concentrated lotion with 34 percent DEET, but it has a controlled-release formula that's designed to deliver protection over a 12-hour period. Although it's pricier than spray mosquito repellents, users at Amazon.com and REI.com say a little bit goes a long way. Most users describe this product as highly effective against mosquitoes, with many noting that it kept them completely bite-free in regions ranging from the jungles of Tanzania to the Alaskan tundra. They also say that the lotion formula is highly sweat-resistant, so it doesn't need to be reapplied that often, and it has no unpleasant odor.
Users' main complaint about Ultrathon is that it feels greasy and unpleasant on the skin. Many say that it leaves behind a sticky, waxy film that's hard to remove, even in the shower and since DEET only repels mosquitoes and ticks, other insects, such as gnats, tend to get stuck in the goo. Still, user reviews are largely positive -- 4.5 stars based on more than 700 reviews at Amazon.com, for example. However, Ultrathon hasn't been tested by the most reliable experts, so there's no scientific data regarding its short term effectiveness or its staying power compared to other DEET-based products.