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Insect repellents

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Are DEET-based repellents the ones to beat?

DEET-based insect repellents are the gold standard for insect repellents. But they have their downside. So are the alternatives catching up? We tested 4 DEET and 3 non-DEET products.

From our test

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About our test

We tested 4 products containing varying amounts of DEET and 3 non-DEET repellents.

Two of the non-DEET products contained a synthetic repellent (picaridin) and one used a “natural” repellent, citronella oil.

6 insect repellents in our test were aerosol sprays and one was a wrist band. They claimed to be effective from 3 to 6 hours.

The test

Each repellent was tested on 4 volunteers in a laboratory. Each volunteer had a specified amount of repellent spread evenly on one forearm, while their other arm was left untreated as a control. Both arms were placed in a cage containing around 50 hungry mosquitoes for a set number of exposures depending on the product’s claimed length of effectiveness.

At each exposure the lab counted the number of mosquito “landings” and “probing of the skin”. These exposures lasted 1 minute and took place at intervals of 15, 120, 180, 240 and 360 minutes depending on the claims of the repellent (the Bushman repellents claimed to last longer than 6 hours). Each mosquito was removed before biting took place.

What we found

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Types of repellent

The US organisation Centers for Disease Control and Prevention (CDC) lists DEET, picaridin and lemon eucalyptus oil as effective insect repellents.

DEET

DEET (N,N-diethyl-m-toluamide) is the most commonly used repellent. It has a long history of safe use and the EPA has found DEET safe when it’s used according to the product’s directions. The CDC says repellents containing DEET are safe to use on children over the age of 2 months. However, the American Academy of Pediatrics (AAP) has recommended DEET levels of no higher than 30 percent when used on children.

The concentration of DEET in a repellent can go as high as 80 percent (concentrations above 50 percent may last longer but provide no added protection). You shouldn’t use too much of it or for too long and you shouldn’t apply it over broken skin or under clothing. Never spray insect repellent directly to your face; instead spray it into your hands first and rub it on. Wash your skin with soap and water after coming indoors.

In more than 50 years’ use there have been fewer than 50 cases of significant reactions to DEET, and these are usually associated with swallowing the repellent or with long-term heavy or whole-body use. But some people could experience skin problems, especially if they use it in high concentrations or in large quantities for several days. DEET may damage synthetic fibres and plastics.

Picaridin

Picaridin is a relatively new repellent that’s less aggressive than DEET. It has little odour, doesn’t feel sticky or greasy, is less likely to irritate the skin, and doesn’t damage plastic.

Lemon eucalyptus oil

Lemon eucalyptus oil is the most effective natural product. We weren’t able to include a lemon-eucalyptus-oil repellent in our test.

The CDC warns that its recommendation on lemon eucalyptus oil’s effectiveness applies only to repellents containing the oil as an ingredient – pure oil of lemon eucalyptus (essential oil not formulated as a repellent) hasn’t been tested for safety and efficacy.

Other natural repellents

Other natural repellents use plant oils with known or suspected insect-repelling capabilities – such as citronella, melaleuca, lemongrass, eucalyptus or lavender.

We’ve found in past tests that they have some initial repellent effect but it diminishes rapidly. If you prefer to use a natural product, you need to reapply it regularly. And never rely on it where there’s a risk of insect-borne disease such as malaria or dengue fever.

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