Does Dish Soap Kill Roaches?

There is a secret the pest control professionals don’t want you to know; some cockroach solutions are right there in your own home. From bathroom chemicals to household cleaners, remedies for roaches are usually right at hand. This assumes you only dealing with a stray American cockroach and not an entire cockroach infestation, but nevertheless, the simplest way to get rid of cockroaches may be a soapy solution.

Key Points:

  • Simple soapy water can be used as an effective method to kill cockroaches.
  • Soap disrupts a cockroach’s protective waxy layer, making them more susceptible to other repellents and toxins.
  • To get the best results, use a liquid soap with a concentration of no less than 32% and apply it directly onto roaches.

Will Water and Soap Eliminate Roaches?

As unbelievable as it sounds, simple soapy water does act as a roach killer if it is a high enough concentration and applied thoroughly. The myth is that the female cockroaches that lay eggs are reliant on filthy bacteria to keep them healthy, and the soap deprives them of this protective bacteria. While this isn’t 100% accurate, it does contain some truth.

The first way that soapy water can kill German cockroaches and other common roach species is it will block their spiracles which allows air past the exoskeleton. This method is only effective if the spiracles are fully covered and unable to open and close, which will suffocate a single roach in a very short amount of time.

If the airways become unblocked or the roach can get in the water, it is possible it will survive as there are few long-term repellent effects and no residual toxicity in soapy water. 

Soap water is also one of the best remedies for roaches because it can remove the waxy layer on a roach’s exoskeleton, which leads to extreme water loss and increased toxin susceptibility. Without this protection, individual cockroaches become much easier to kill, and any other remedy for roaches, like diatomaceous earth or boric acid, instantly becomes more effective. 

Is Soap A Good Roach Poison?

Dead Roach

Soap can be a good roach poison if it is used correctly, but in general, bars of soap and some soap powders can also be a food source for desperate roaches. While a professional exterminator won’t recommend it, especially for a bad cockroach infestation, soap with water is a cheap and effective roach killer. When applied correctly, this harmless chemical pest control method can keep your kitchen and bathroom roach free. 

For the best results, make sure the mixture is at least a 32% or higher concentration of soap for reliable results. Cockroaches are tough pests, so a weak mixture of soap will not be effective. Other readily available products like boric acid, alcohol, cinnamon oil, lemon, and vinegar can be added to make the mixture even more deadly to pests. 

Soap containing baking soda, borax, tea tree, or other natural insecticides can poison roaches even in dry or powder form and, when added to a sugar mixture, can wreak havoc on a cockroach’s abdomen. Borax and sugar mixtures are common bait in cockroach traps used by an exterminator.

Instead of toxic insecticide sprays, soap water is a safe and effective method of control as ingesting small amounts of soap generally won’t harm children and pets and with no risk of poisoning through accidental contact. 

Soap Pesticide Techniques

Unfortunately, setting a bar of soap in the bathtub will not stop common household cockroach species. To inflict mass cockroach destruction with nothing but soap, you will need to make a spray or other mixture to increase the potency. Other soap remedies for cockroaches include using shavings, powder, and certain types of soap bars. Liquid soap, like dish soap or highly-concentrated hand soap, can be a very effective homemade roach killer. 

Type of SoapPreparationUse
LiquidAdd some water to make it sprayableSpray directly on larger roaches or place around gaps where roaches enter
BarShave or dissolve in hot water to prepare a useable solutionSpray on roaches or drop the occasional roach into the solution to kill them instantly 
PowderNatural roach killer dust made of borax and soap powder Attracts roach with soap as a food source and kills completely with the addition of borax


Using soap in a liquid form is far more concentrated and does a better job of killing roaches. Unlike gentler body soaps, liquid dish detergent is made of harsher soaps and is more effective than a diluted soapy water solution. Concentrated liquid soap squirted directly onto roaches will end them immediately. 


Bar soap needs to be processed the most to make it of any use against roaches. Melt a 1/2 cup of bar soap and mix it into 1 cup of water then, you can add it to a spray bottle or pour on roaches. Make sure the concentration of soap is over 32%, and sprayed roaches should be dead within 24 hours, a weaker formulation may still kill roaches, but it isn’t guaranteed. Soap that is used on our faces and bodies can be far more gentle than the harsh chemicals in other soaps.

Some bar soaps contain other plant-based ingredients with insecticidal properties, making them a good option when choosing which soap to use as a remedy for roaches. 


Soap in powder form is easy to sprinkle but not usually harmful to roaches when ingested. Powder soap has a lower fat content than bar soap, so not as attractive as a food source for hungry pests. Additionally, soap powder can be mixed with borax or other agents if you want to add freshness and kill roaches faster. It also easily dissolves in water at high concentrations to make a powerful roach soap spray in seconds.

Will Soap Have Any Residual Effect on Roaches?

Female german cockroaches are more resilient to soap and water than males and cockroaches of other species, but they still can be killed. Because female roaches live longer than males and are responsible for laying eggs, they have developed additional resistance to chemicals. Since soap suffocates and doesn’t need to poison the roaches like other pesticides, it is harder for females to survive or adapt to not being able to breathe.

In some cases, common German roaches will eat soap if no other food is available due to the high levels of oil and fat, meaning its residual effects are scant or non-existent. Unless insect toxins are present in the stored soap, such as peppermint or citronella, it will not be harmful if ingested when dry like powder or as a solid bar. Dish soap will kill roaches with reliability if applied directly and formulated strongly enough.