The Top 5 Reasons why Bed Bugs Defy Insecticide Treatment


Top 5 reasons why bed bugs defy insecticide treatmentsBed bugs are becoming more common during recent years, and this could be due to one reason – their thicker skins!

Researchers at the University of Sydney have discovered that bed bugs showing resistance to commonly used insecticides have thicker skins compared to those that are rapidly killed by chemical treatment. (Lily, 2016).

Thanks to Rentokil’s Entotherm solution, which makes use of heat treatment to kill bed bugs and other insects, no chemical treatment is required (more about this later).

The unwelcome return of the bed bugs

In previous years, the presence of bed bugs was a rare occurrence; even for a pest-control technician. Over the past two decades, these parasites have reappeared. In 2005, they were reported as being common again in the urban environment in the US, Europe and Australia, infesting apartments, hotels, healthcare facilities and college dormitories (Romero, 2007).

Bed bug infestations impacts us in the following ways:

  • Through annoying bed bug bites.
  • Incurring unnecessary costs: bed bugs infestations result in on-going monitoring, treatment of bed bug infested rooms and furnishings, and potential disposal and replacement of infested items.

Reasons why bed bugs defy treatment

  1. Repeated use of insecticides: A study in the US in 2007 found “extremely high levels of resistance” to common insecticides in multiple infestations across the country. It concluded that resistance was the “expected outcome of their repeated use”.
  2. Bed bugs spread between rooms and furniture: The failure of insecticides to quickly control bed bug infestations of resistant insect populations increased their opportunity to spread between rooms and buildings, and by recycling of furniture and bedding (Romero, 2007).
  3. Increased global travelling: The increase in international air travel has also meant more people travelling to and from infested areas, giving them more opportunity to spread — often in the luggage of travelers, as many an hotelier has found out.

    Find out how to prevent bed bugs when traveling

    Find out how to prevent bed bugs when traveling

  4.  Changes in the use of insecticides: The way insecticides were used also thought to have contributed to growing resistance. This includes the more controlled application of insecticides, instead of widespread spraying, and the move away from organochlorines such as DDT. Pesticide resistance was, however, first noticed with the use of DDT in the 1950’s.
  5. Bed bugs have the ability to adapt: Studies of other insects have shown that they can develop a range of adaptations that confer pesticide resistance following exposure to treatments, including metabolic changes, increase in proteins and fats that bind to the pesticide chemical and a thicker cuticle (insect ‘skin’) acting as a barrier to the pesticide entering the insect body. No previous research, however, had shown that pesticide-resistant bed bugs had a thicker cuticle. (Read more about the research below).

Bed bug research findings: Cuticle thickness plays an important role in resistance

The researchers at the University of Sydney collected bed bugs from an infestation in a house and bred them in their lab to produce a group that were all the same age and had the same diet and conditions.

  • They were placed on an insecticide-treated surface and removed as they were ‘knocked down’.
  • They were separated into three groups that were knocked down within 2 hours (called intolerant), 4 hours (tolerant) and those that were unaffected after 24 hours (resistant).
  • The researchers then measured the cuticle thickness of the bed bugs by imaging cross sections of the bed bug legs using an electron microscope and drawing the boundaries of the cuticle on the image to measure the thickness (see figure 1).
Electron microscope image of a cross section of the leg of a bed bug (Cimex lectularis) showing measurement of cuticle thickness.

Figure 1. Electron microscope image of a cross section of the leg of a bed bug (Cimex lectularis) showing measurement of cuticle thickness.

In summary:

  • They found that the length of time the bed bugs survived the insecticide treatment was related to the thickness of their cuticles. The cuticles of the most resistant group were on average 16% thicker than the intolerant group.
  • The results of this research suggests that an integrated pest control approach is required to prevent the spread of resistant bed bugs.
  • They also conclude that the combination of adaptations to pesticides shown by bed bugs — the metabolic and physical changes — have important consequences for the formulation of insecticides in bed bug control.

Savvas Othon, Service and Science Innovation Director at Rentokil Initial, commented, “There is no doubt that Bed Bugs have evolved thicker skins as detailed by the university and as we know, changes to morphology through evolution are triggered, in the main, by a need to survive and adapt to the environment. The wide use of chemicals could be such a trigger, however this is hypothetical and will need further clarification, for example, mapping of historical bed bug samples to the level of insecticide use over time. Whether the evolution was triggered by insecticide use or not, the correlation between cuticle thickness and resistance is an important find and it may have implications on current treatment methods. For example, we could see the increased use in desiccant dusts to impact the insect cuticle as a compliment to insecticide treatments“.

Resistance is futile! Rentokil’s Entotherm Treatment turns up the heat

These blood-sucking pests are like something out of a scary movie, evolving to a point where us humans have a serious problem on our hands. Of course, Rentokil’s Innovation team have a brilliant counter strategy in place for these think-skinned bed bugs – the Entotherm Treatment.

Rentokil has developed a chemical-free method of pest control that is effective in getting rid of bed bugs and other insects such as cockroaches, including those that have resistance to pesticides. Our Entotherm heat treatment won a Best Business Award for Best Innovation in the private sector. It uses a heat regime to kill insects — eggs, larvae and adults — and can be applied to a room or to items such as furniture placed inside a special pod. Treated areas can be re-used immediately after treatment with no residual side effects.

Entotherm treatment.

Find out more information about how to remove bed bugs using our Entotherm treatment.


  • Lilly, j. G. (2016, April 13). Cuticle Thickening in a Pyrethroid-Resistant Strain of the Common Bed Bug, Cimex lectularius L. (Hemiptera: Cimicidae). PlosOne.
  • Romero, A. (2007). Insecticide resistance in the bed bug: a factor in the pest’s sudden resurgence? Journal of Medical Entomology, 44(2), 175-8.
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