does soap and water kill cockroaches?

Does Soap Kill Cockroaches?

Cockroaches are notoriously difficult to kill. You may not own the proper chemicals to kill them, nor have the budget to hire an exterminator. That’s led to several urban myths about DIY home products that kill roaches. Soap and water is touted as an effective roach killer.

Soap can be used to get rid of cockroaches. A soap and water mixture can melt away a roach’s protective outer coating and block their spiracles. Unable to breathe, the insects will eventually die. However, both male and female cockroaches differ in their vulnerability to soap.

Keep in mind that soap itself won’t kill roaches; it’s how you use it. These bugs are capable of eating bar soap, so it’s clearly not toxic. Be sure to mix the soap with water, use it in a spray bottle, and properly coat each roach. Even once this is done, be aware that it doesn’t have a 100% success rate. Other methods will definitely be needed to remove a large infestation.

Does Soap and Water Kill Cockroaches?

Soap is able to kill roaches. However, for the most effective results, you should mix the soap with water. That’s because it:

  • Can be easily transferred to a spray bottle
  • Covers a wider surface area
  • The water can help the soap better sink into a cockroach’s spiracles

That was proven in a study published in Advances in Biological Science Research. Here, American cockroaches were exposed to 5 sprays of soapy water from a spray bottle, at 32% concentration. More than 50% of the roaches were dead within 24 hours. Soapy water with higher concentrations yielded similar results.

Liquid dish soap was found to be just as effective. According to the Journal of Economic Entomology, a 3% concentration of soapy water mix left 100% of German cockroaches unresponsive in only 3 minutes.

Does Soap Kill Male Roaches Better Than Females?

As it turns out, mortality for male and female cockroaches differs slightly from each other. According to the Journal of Economic Entomology, it was found that adult German cockroach females are the most resilient against a soapy water solution.  

Additionally, the International Journal of Scientific Research notes that male cockroaches, on average, have shorter lifespans than female cockroaches.  This may be a result of evolution. Females are primarily responsible for laying eggs, and thus, their future generations. They may have evolved to be more resilient against treatments as a result.

This finding was only observed in German cockroach females. It may not apply to other common household cockroach species.

How Does Soap Kill Roaches?

While the soap-and-water fix isn’t a myth, there are still myths surrounding why this solution works. Some believe it’s because soap is designed to kill bacteria. Since roaches are dirty creatures attracted to dirty areas, you’d assume that they can’t stand it. However, that’s not the case.

Soap Harms A Roach’s Protective Coating

A large majority of insects produce an oily and waxy outer coating. This cover acts as a protective surface against bodily harm. It also helps the cockroach maintain hydration and repel water off its body.

When you put soapy water onto a cockroach, the soap removes this protective, waxy film. This leaves them vulnerable to extreme water loss and water damage.

killing cockroaches with soapy water

Soap Suffocates Cockroaches

Furthermore, roaches have a unique respiratory system. Instead of lungs, they have spiracles. These breathing passages allow them to take in oxygen and expel carbon dioxide. With an ability to close these spiracles, they can avoid drowning. However, soapy water disrupts this.

A soapy solution is able to coat and block these spiracles. Try as they might, cockroaches will struggle to open or close them once they’re fully coated. This hinders their ability to breathe. If sufficiently covered in soap, roaches will be entirely unable to draw air.

This ultimately results in death. In fact, it’s one of the only ways to properly suffocate a roach.  

Do Roaches Like Soap?

You may be surprised to learn that cockroaches like soap. In fact, they’ll eat the substance if there is no other food available. That’s because bar soap, in particular, is made with ingredients such as fat and oil. This gives it a moisturizing effect on the skin, a pleasant smell, and even some medicinal benefits. For a roach, however, these ingredients also contain:

  • Carbohydrates
  • Protein

In particular, bar soaps contain many carbohydrates. This substance is highly desired in a cockroach’s diet. According to the National Library of Medicine, it helps them retain nutrients and boosts male pheromone release. The latter is very important for attracting mates, and consequently, the survival of their population.

So it’s not the soap itself that cockroaches want. Yet, if no other food can be found, they will seek out the bar soap in your bathroom.  

The more organic or natural the soap, the better. Nibbling on soap will cause a roach no harm. If they are coated in the substance, that changes.

What Type of Soap Kills Roaches?

If you want to kill roaches using household soap, then you have two options:

  • Bar soap
  • Liquid dish soap

The main difference between the two is the additives that make up each.

Bar Soap

Soap bars are packed with additives that work primarily as good scents and skin softeners. To create your own roach poison with it, you can start by:

  • Mixing 1 cup of water
  • With 0.4 cup of melted bar soap
  • Pouring this mixture into a spray bottle

Be sure to make it a concentration of 32% (or higher). At this intensity, there’s a high chance that any sprayed roaches will die within a day.

Liquid Soap

While bar soap and liquid dish soap are both effective against cockroaches, the liquid kind may be the best. Its additives function to cut through heavy grease and kill bacteria. Because of this, it tends to be a lot harsher.

Liquid soap is also easier to mix with water and use in a spray bottle. If you don’t want to melt down bar soap, then liquid options are best.

Since liquid soap is more chemically processed, it contains fewer fats or oils. As such, unlike bar soap, it won’t attract any roaches while lying around. You only need:

  • 1 cup of water
  • 1 ½ teaspoon of liquid dish soap
  • Mix these together in a spray bottle

How To Kill A Roach With Soap

When you encounter a cockroach, remember to:

  • Shake your soapy water solution before spraying. The more incorporated the soap is, the more effective it’ll be.
  • Give the roach several sprays. This will ensure that enough of it gets onto the cockroach.

These insects are persistent, so be persistent back.

Is Soap A Good Roach Poison?

Soap and water may appear too simple to be an effective pesticide. However, as shown above, it does work in a limited way.


Here’s why soap might be your first choice:

It’s Non-Toxic

Soap is not toxic to animals and people in small quantities. That makes it great for those who have pets in the home or young children.


Soap is readily accessible in most grocery or convenience stores. Some can be purchased for less than $1. This makes it ideal for people who don’t have the current funds for:

  • Insecticides
  • Hiring an exterminator

Found Anywhere

Hardware stores usually sell the widest range of cockroach-eliminating chemicals. If you don’t have access to one, that’s a problem. In contrast, soap is more common than bug poison, so you can find it nearly anywhere.


Those perks aside, these elements can drive you away from soap:

Not 100% Effective

Studies proved that different cockroaches react to the soap in different ways. If you spray an American cockroach, it may have a 50% chance of surviving. German cockroaches, however, are more susceptible.

Many commercial pesticides, even found in stores, promise a higher kill rate. They often won’t discriminate against the type of cockroach either. If you’re unwilling to give any roaches a 50/50 shot at living, then consider more traditional methods.

Can’t Handle An Infestation

If you’re dealing with one or two roaches, soap and water works. With that said, you can’t handle a full infestation by killing a single roach at a time. You’ll need to take more drastic measures.

Requires You To Be Present

While it’s also the case with insecticide sprays, this soap-and-water method requires you to be present to kill the roach. Because this insect mostly comes out at night, you may not be able to properly combat it by hand.

All in all, soap and water can kill roaches. Just be sure to consider your situation, and decide if more extreme methods are needed.