The label is the operating instruction
The HSE says you must read and understand a biocide label before use. You must also follow its instructions with care. Household insect sprays are biocides in UK law, so this rule applies to every bottle and can.
A label shows an authorisation or approval number, and only authorised products can carry one. It also says what the product is for, who may use it and how much to apply. It covers where to put it, how often, how to store it and how to throw it away. The HSE adds that a biocide must not be used for any other purpose.
Who may use which product
Some products are for the public. However, others are only for trained professionals. The HSE says the public must never use professional-only products, because professionals need training first.
That training covers the law, correct use and risk assessment under COSHH. It also covers protective gear. The HSE suggests that non-professionals consider hiring a pest controller. The NHS gives the same advice and points you to your local council. Our safety and labels guide goes through the label step by step.
Residual action needs the right placement
A residual product keeps working after it dries. Insects that cross the treated spot later pick up the active ingredient. Heat and steam cannot do this, which is why sprays and dusts still have a place.
However, placement decides the result. University of California advice says pesticides are not usually applied to mattresses or bedding because of the risk to people. It also says dusts can give long-term control when they go in dry places such as under baseboards. A study in US apartments found that adding a silica gel dust to a non-chemical plan cut counts by 99% over six months, against 89% without it. See our desiccant dust guide for more.
Resistance changes the plan
Resistance is a real problem. A published review says pyrethroids were the mainstay of bed bug control for decades. It reports rising tolerance and a growing number of control failures. The NHS also warns that bed bugs may be resistant to some insecticides.
A lab study adds another reason for the difficulty. Bed bugs took up less of one insecticide into their bodies than cockroaches did. The authors say this may be one more reason bed bugs are so hard to control. Our resistance guide explains how this affects product choice.
What insecticides cannot do alone
A review in a clinical journal calls bed bug control challenging. It advises a mix of non-chemical methods and careful use of insecticides. The same review warns that misuse of chemicals can harm human health.
University of California advice says total-release foggers are ineffective for bed bugs and can harm residents. Our guide to why foggers fail covers this. Moreover, steam did as well as a spray in one simulated field study, so a treatment comparison is worth reading before you buy a spray. Our guide to shop-bought sprays covers what the evidence says on that.
Judging whether a spray worked
Do not expect every bug to die at once, because some insects hide away from the treated spot. Our guide to how long bugs take to die after treatment explains the usual pattern. Check again on a set schedule before you judge the result.
Products also differ in speed. University of California advice says pyrethrin gives a quick knockdown but little long-term control. It adds that some newer products may take many days to kill bed bugs. Because of this, ask your provider when to expect results and when to check.
Interceptor traps under bed legs give a count you can track. Looking alone often misses bugs when only a few remain, so traps add proof. Read the after-treatment guide to set up a simple check routine.
Sources and further checks
Open each source before you act on anything that can change, such as council services, prices, tenancy rules and product labels. Labels and official guidance are revised from time to time, so the source always wins over our summary.