Shop-bought sprays rarely clear a bed bug infestation on their own. Some kill the bugs they touch. However, few reach the cracks where most bugs hide, and many bed bugs now survive the common active ingredients. A spray can play a small part in a plan. It is a poor plan by itself.
This post sets out what the research says, how UK label rules work, and what to do instead.
Why a spray is only half the job
A contact spray kills insects it lands on. A residual spray is meant to leave a film that kills bugs that cross it later. Both need to reach the bug or its route. Bed bugs spend most of their time in seams, joints and gaps. They do not sit on open surfaces. A quick spray over a mattress therefore misses most of them, because they are tucked out of reach.
Our insecticides guide explains the difference between contact and residual action. It also explains why placement matters more than volume.
Foggers: the clearest evidence
Total-release foggers, sometimes called bug bombs, have been tested directly. In a US laboratory study, field-collected bed bugs showed little or no harm after two hours in the fog from three over-the-counter fogger products. Even a pyrethroid-susceptible lab strain survived when it had a thin cloth to hide under. The authors found minimal insecticide penetration into typical hiding places. They concluded that foggers should not be recommended for bed bugs.
The reasons are simple. The mist does not reach the harbourages, and many bugs resist the low dose anyway, since resistance is common. Read why foggers fail for the full explanation. The foggers in that study used pyrethrins or pyrethroids, so resistance and poor reach worked against them together.
Resistance blunts many sprays
Pyrethroids have been the mainstay of bed bug control for decades. A review of the evidence found that increasing tolerance to them is causing control failures. The same review linked the modern resurgence in Europe, the USA and Australia partly to resistance. Those are the same chemical families the fogger study tested.
The NHS makes a similar point. It says bed bugs are very difficult to remove yourself because they are hard to find and may be resistant to some insecticides. Our page on treatment resistance shows how resistance changes the plan, for example by adding physical methods.
What about natural sprays?
Plant-oil sprays sound safer, and some are less toxic to people. Safer is not the same as stronger, though. In one laboratory test of eleven non-synthetic products, only two caused more than 90% nymph mortality. Those two still did worse than the conventional comparison sprays in a test where bugs could choose which surface to cross.
A field trial in apartments gives a realistic picture. A plant-oil product cut bed bug counts by about 92% after 12 weeks, similar to a conventional spray. However, bed bugs were eliminated from only 22% of the treated apartments. So a large drop in numbers still left most homes infested. Dusts raise similar questions, which we cover in our post on diatomaceous earth at home.
The UK label rules
Under HSE guidance, anyone using a biocide at home is responsible for using it correctly. You do not need training to use a product made for the public. However, you must follow the label instructions carefully. The label should show an authorisation or approval number and what the product is authorised against. It should also say who may use it and whether you need protective equipment.
Never use a product meant only for professionals. Professional users must have the right training and, for some products, certification. HSE also says that if you are not a professional, you should consider using a professional pest controller, and your local council is one place to start. Our safety and labels guide walks through what to check before you open a bottle.
If you still want to use a spray
Keep it simple and safe:
- Check the label names bed bugs, or a use that clearly fits.
- Follow the dose and surface instructions exactly.
- Never mix products or add extra concentrate.
- Keep it off skin, clothes and bedding unless the label allows it.
- Keep children and pets away for the stated time.
Repeated unsupervised spraying can also make later assessment harder, because you no longer know which product the bugs have met. Our DIY guide lists other stop points.
What works better
Start by confirming the insect. Then monitor, so you know how widespread the problem is. Our post on preparing a room for treatment shows how to get ready. For a firm result, compare methods in our treatment comparison. A properly run heat treatment is one option, and a professional insecticide programme is another.
After any treatment, judge progress by evidence rather than by one quiet night. How long after treatment bed bugs die explains the realistic timeline. If you choose steam for parts of the job, read about steaming a mattress first. Finally, a good mattress encasement can help you trap and monitor bugs in the bed.
Sources
- Jones SC, Bryant JL (2012). Ineffectiveness of over-the-counter total-release foggers against the bed bug. Journal of Economic Entomology.
- Davies TGE, Field LM, Williamson MS (2012). The re-emergence of the bed bug as a nuisance pest: implications of resistance to the pyrethroid insecticides. Medical and Veterinary Entomology.
- Singh N, Wang C, Cooper R (2014). Potential of essential oil-based pesticides and detergents for bed bug control. Journal of Economic Entomology.
- Wang C, Singh N, Cooper R (2014). Efficacy of an essential oil-based pesticide for controlling bed bug infestations in apartment buildings. Insects 5(4):849–.
- HSE. Using biocides: overview.
- NHS. Bedbugs: how to get rid of them.