Which? Test Reveals Expensive Mosquito Repellents Fail to Protect Against Heatwave Surge

Following months of erratic weather, experts warn that Britain's recent heatwave could trigger a surge in mosquito populations.

What was once a holiday nuisance is now a growing domestic challenge as summer temperatures rise.

New research by Which? reveals that high prices do not guarantee superior protection against these biting insects.

The investigation found that some expensive repellents fail within minutes, while a budget option offers lasting defense.

Twelve products were tested using a rigorous method involving volunteers exposing bare arms to cages full of mosquitoes.

The goal was to measure exactly how long each spray prevented a bite.

Two items performed terribly, failing to protect skin for more than a few moments.

These were the Pestects Mosquito Repellent Bracelets and the Meadows Organic Citronella Spray.

Both are marketed as eco-friendly and safe for sensitive skin, yet their effectiveness was negligible.

Pestects bracelets claimed up to 300 hours of protection but failed in under three minutes during testing.

Sold at £19.99 for a pack of 12, they represented a significant financial waste for consumers.

Meadows Organic Citronella Spray offered little better results despite its natural oil formulation.

Volunteers were bitten almost immediately upon exposure to the mosquitoes.

In stark contrast, Asda's own-brand Extra Strength Insect Repellent spray provided complete protection for 9.5 hours.

Priced at just £4 for a 125ml bottle, it outperformed brands costing more than double the amount.

Natalie Hitchins, Head of Home Products and Services at Which?, emphasized the findings.

She stated that avoiding bloodthirsty insects should not require spending a fortune.

Her tests showed that flashy, pricey repellents can be a total waste of money.

She noted that a simple £4 supermarket spray beats fashionable brands in delivering reliable safety.

Other products also kept volunteers bite-free for the full 9.5-hour duration of the test.

However, none matched the low cost of Asda's own-brand formula.

Experts advise shoppers to check ingredient lists for proven actives like DEET.

This chemical confuses insects and drives them away, serving as the gold standard for repellency.

While effective, DEET can damage plastics and synthetic fabrics, requiring careful application.

The study concludes that effective protection is accessible without paying a premium price.

A recent evaluation by the consumer group Which? identified several mosquito repellents as highly effective, including Jungle Formula Maximum Aerosol Insect Repellent at £7.20, Boots Repel Maximum DEET & PMD Aerosol at £9.10, Pyramid Trek 50 at £9.50, and Lifesystems Expedition Max DEET Mosquito Repellent at £9. While these products delivered strong protection, testers observed that application comfort varied, with some users finding the textures less pleasant or the scents off-putting.

Autan Insect Repellent, priced at £5.65, emerged as a standout performer. Containing 20 per cent picaridin, a synthetic compound designed to mask human scent from insects, it successfully repelled mosquitoes for the full 9.5 hours of testing without a single reported bite. Similarly, Incognito Insect Repellent Pump-Spray, which costs £13.99, performed well despite its higher price point. Utilizing plant-derived PMD extracted from the lemon eucalyptus tree rather than DEET, it provided nine hours of protection and is approved for use on babies from six months of age. For those seeking a multi-purpose solution, Which? noted that Boots Soltan Soothe & Moisturise Aftersun Lotion with Insect Repellent offered 4.5 hours of insect deterrence, making it a viable option for outdoor dining following sun exposure.

The study emphasized that all top-performing products relied on scientifically proven active ingredients rather than vague "natural" claims. In the current hot and humid weather, which creates ideal breeding conditions for mosquitoes, the consumer group highlighted four ingredients backed by robust scientific evidence: DEET, icaridin, PMD, and IR3535. Conversely, the worst-performing products depended on unrefined essential oils such as citronella, lemongrass, or peppermint. While these may offer a summery aroma, they provided minimal actual protection during the tests.

DEET remains the gold standard, particularly for high-risk areas where mosquito-borne diseases like malaria are a concern. Icaridin, also known as picaridin, is considered a powerful alternative; recommended by the World Health Organization for protection against Zika and malaria, it is generally more pleasant on the skin and lacks the reputation of DEET for damaging plastics. DEET formulations typically last between six and eight hours, whereas natural PMD and icaridin formulas require reapplication every four to six hours, or sooner if the user has been swimming or sweating heavily.

PMD stands as the primary "natural" option with credible evidence, derived from the lemon eucalyptus tree and capable of high effectiveness when correctly formulated. However, Which? cautioned consumers not to confuse genuine PMD with ordinary citronella oil or plain, unrefined eucalyptus oil, which are distinct substances that performed poorly in the study. IR3535 is another reliable synthetic repellent, though it is better suited for lower-risk, non-malaria regions rather than destinations requiring stronger protection.

Ultimately, the effectiveness of any mosquito repellent depends on correct application. Experts advise ensuring that wrists, ankles, necks, and hands are fully covered and applying the product only after sunscreen has been set. Additionally, users should spray repellent into their hands first in a well-ventilated area before rubbing it onto their face, remembering to wash their palms afterward to prevent accidental eye contact.