Do all mosquito repellents protect equally well?

Insect bites can be annoying, but they can also transmit disease, so if you're in a higher risk area it's important to take protective measures.

Dengue fever and other mosquito-borne illnesses used to be the preserve of tropical climes, but cases have been on the rise in Europe in recent years due to climate change, making it crucial that you have protection you can rely on even when you're closer to home.

When we put 11 popular insect repellents to the test, including a range of formulas from Autan, Boots, Incognito, Jungle Formula and Superdrug, we found that some performed exceptionally well, while others gave significantly less protection. Which? members can see our top picks in our guide to the best mosquito repellents.

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Why good insect repellent is increasingly important

The UK has more than 30 native mosquito species and although many of these bite, most just cause irritation and discomfort to those affected.

However, growing global travel and trade coupled with climate change means mosquito varieties that carry diseases such as zika and dengue are becoming established in some areas of Europe. 

Exotic mosquito species including the Asian tiger, Asian bush and yellow fever varieties are already collectively established in countries including France, Germany, Spain, Portugal and Italy. In May 2024, the European Centre for Disease Prevention and Control added the Canary Islands (Spain), Slovenia and southern Poland to the list.

Although the UK doesn't currently have any established populations of these pests, experts at the UK Health Security Agency fear they will find the UK climate palatable enough to make it their home before too long.

The NHS website warns that countries where dengue fever has been found include Croatia, France, Italy, Spain, Portugal and Madeira.

What to look for when choosing insect repellent

Research shows you should use a repellent containing one (or more) of the four active ingredients that are scientifically proven to repel mosquitos: DEET, IR3535, icaridin or PMD (although IR3535 products should only be used in non-malaria areas).

Tropical repellents are designed to repel more aggressive mosquitoes that carry diseases such as malaria and dengue, using higher concentrations of active ingredients.

Official UK government advice for travellers to tropical destinations is to use a 50% DEET product as a first choice or, if this isn't tolerated, a repellent containing the highest strength formulation available of either icaridin at 20%, PMD or eucalyptus citriodora oil.

The most effective tropical formulations we tested were ones containing DEET, with the best achieving an impressive overall test score of 92%. 

We also found that containing a proven repellent ingredient wasn't a cast-iron guarantee that a product would protect well. Some products containing the same active ingredient performed better than others, so the formulation matters too. 

See which mosquito repellents we recommend, including the best non-DEET products, in our mosquito repellent reviews.

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Our mosquito repellent tests

There's no better test of how good a repellent is than getting real-life mosquitos on the case, which is exactly what we did in our Which? tests.

We used the blind 'arm-in-cage' method, where volunteers have mosquito repellent applied to their arms but don't know which product they are using.

They then put their arm into a box full of live mosquitos for a set amount of time before removing it to check for bites. 

This is repeated with checks every half hour until a mosquito bite is confirmed – the longer the protection against bites, the better the product is.

We used multiple testers to check how consistent protection is across different users. Some products proved highly consistent, while others were much more variable in how well they protected people.

Mosquito need-to-knows

Always check the specific risks of the area you are travelling to so you know how best to protect yourself. Some mosquito varieties are more active at dusk, while others are also active during the day.

Generally, mozzies favour hot and humid weather with little to no wind. Be particularly on your guard near bodies of still or slow-moving water, such as rivers, lakes and ponds. 

If you feel unwell after getting bitten, particularly if you have a fever, temperature, nausea, a rash or muscle aches, seek medical advice and flag where you've been and the fact you've been bitten.