Bed Bugs Are Becoming Harder To Kill in the UK As They Become Resistant to Insecticides

Bed bugs are becoming increasingly difficult to eliminate across the UK as the insects develop resistance to the insecticides once relied upon to kill them, according to pest-control experts.

The growing problem is becoming a leading cause of treatment failures, forcing pest controllers to rely more heavily on alternative methods such as heat and steam, while experts warn that ineffective DIY treatments may be making infestations even harder to eradicate.

The warning comes as infestations continue to rise across the country. In one London borough, which has asked to remain unnamed, officials recorded 155 bed bug cases in the first six months of the year, a 50 per cent increase compared with the same period in 2024. Nationally, infestation numbers are reported to have doubled since international travel resumed following the pandemic, highlighting the growing challenge facing pest controllers as conventional insecticides become less consistently effective.

When the Usual Chemicals Stop Working

For pest controllers, the rising number of infestations is only part of the challenge. According to James Roades of ThermoPest, bed bugs themselves are becoming more difficult to eliminate as resistance to conventional insecticides continues to grow.

'Insecticide resistance is now a leading cause of control failures,' Roades said.

Roades said insecticides that once reliably controlled bed bugs are increasingly failing as resistant populations become more common, forcing pest-control companies to adapt how they respond to infestations. As conventional sprays become less dependable, firms are increasingly relying on non-chemical methods, including heat and steam treatments, alongside monitoring lures, to tackle infestations that no longer respond to traditional insecticides.

ThermoPest said demand for its services has risen sharply as more households find themselves unable to eradicate bed bugs using conventional treatments alone.

While the return of international travel has helped drive the resurgence of bed bug infestations, experts say insecticide resistance is now making those infestations significantly harder to bring under control once they become established.

Bed bug expert Chow-Yang Lee said resistance develops through a process of natural selection. Each round of insecticide treatment kills the insects most susceptible to the chemicals, while those able to survive continue to reproduce. Over successive treatment cycles, resistant bugs account for a greater share of the population, leaving entire infestations far less vulnerable to insecticides that were once effective.

Lee said early detection remains critical because delaying treatment gives bed bugs more time to multiply and spread into neighbouring rooms or properties, allowing resistant populations to become more firmly established before action is taken.

DIY Treatments Could Make the Problem Worse

The rise of insecticide-resistant bed bugs comes at a particularly difficult time for households facing continued cost-of-living pressures. In an effort to avoid the expense of professional pest control, many people have turned to shop-bought sprays, aerosols and foggers to tackle infestations themselves.

Lee warned that incomplete or ineffective treatments can unintentionally reinforce the very problem they are intended to solve.

By killing only the insects that remain susceptible to insecticides while allowing resistant bugs to survive and reproduce, partial treatments can leave homeowners facing larger infestations that are even harder to eradicate with conventional chemical products.

Experts say early intervention and thorough treatment remain the best way to prevent infestations from becoming established before resistant populations take hold. As insecticide resistance increasingly undermines the effectiveness of conventional chemical treatments across the UK, they warn that relying on quick DIY fixes may ultimately allow infestations to become more persistent, more difficult to eliminate and more expensive to resolve.