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 US Environmental Protection Agency (EPA) has found DEET safe when it’s used according to directions. The CDC says repellents containing 30 to 50 percent DEET are safe to use on children over the age of two months.

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.

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.

Tip: The EPA has expressed concern about products that combine DEET with sunscreen. DEET should be applied sparingly and not reapplied too often, while sunscreen products recommend frequent reapplication – so regular applications of sunscreen may mean you use more DEET than necessary. Mosquitoes are also generally more active in the early morning or evening, times when you are less likely to need sunscreen.

Picaridin

Picaridin is a relatively new repellent that’s less aggressive than DEET. It 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 find a lemon-eucalyptus-oil repellent to include in our test but a Consumer Reports test in the US found it to be as effective (against mosquitoes) as low-concentration DEET products.

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 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, lemongrass, eucalyptus or lavender.

We’ve tested natural repellents before, in 2000. Both then and now we’ve found 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.