Pest Control

Can Instant Mashed Potatoes REALLY Kill Rats? (We Find Out)

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For over a millennium, rats and other rodents have terrorized society by spreading deadly diseases all around the globe. Rats and mice are responsible for circulating over thirty-five different viruses, which have caused more deaths than all the wars waged combined.

Instant mashed potato mix, better known as potato flakes, can kill rats because the bits expand in size when mixed with water. Having these flakes expand inside a rat’s stomach will not allow any new foods to enter. Because a rat cannot vomit, it can’t get the potato mix out.

To ensure we prevent ourselves and our loved ones from falling victim to a disease carried by a rat, we must do everything we can to rid our homes of these pests. Would you be amazed if we told you that you could weaponize instant mashed potatoes to fight against disease?

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The Theory Behind Instant Mashed Potatoes Killing Rats

Before we delve into the rest of this article, we need to understand why some people on the internet believe that you could use instant mashed potatoes to kill rats.

For nearly a decade, online users have discussed the possibility of using instant mashed potato flakes to kill rats more humanely, an alternative to traditional poisons and death traps.

Their theory was that if you put out these dried potato flakes, rats would eat the flakes, thinking it was food, and the rat would get thirsty and look for a water source. Once the rat drank some water, the instant mashed potato flakes would absorb the water and begin to expand inside the rat’s stomach, killing it instantly, or maybe they are allergic to some of the ingredients in instant mashed potato products.

The rationale for swapping out poison for instant mashed flakes is if a stray animal or pet came across the now deceased rat and mistook its body as an easy meal, it wouldn’t harm them.

The instant mashed potatoes bring about the rat’s demise but aren’t harmful to larger animals.

The actual question is, does this theory hold any truth, or is it all a load of instant mashed lies?

What Is Instant Mashed Potatoes?

Instant mashed potato products are flat chunks of dehydrated mashed potato. These ‘flakes’ are produced by cooking and crushing the potatoes in between rollers on the surface of a drum and then fast-dried until the crushed, mashed potato reaches a specific humidity level.

The dried mashed potato is scraped off the drum, and the sheet is broken up by a mill sifter into smaller flakes and packaged.

The cells that initially made up the potato are damaged during production. The reconstituted product’s texture is kept stable using an additive, a monoglyceride emulsifier, and subsequent cooling. This procedure was first used in Philadelphia between 1953 and 1959 and has been implemented worldwide.

Instant mashed potato flakes are relatively easy to rehydrate because the potato starch retains most of its absorbency because of how quickly the chips are dehydrated in the production process.

Are Rats Picky Eaters?

Rats are very particular about the food they eat. They do not possess the ability to regurgitate whatever it is they consume. So when they encounter food that they are unfamiliar with, they will only nibble on a small amount and wait more than a few hours to see if the food has any adverse effects before consuming more. Studies have shown that rats will avoid food that changes their physiological state.

Do Rats Have Food Allergies?

Rats are not genetically engineered to be immune to food allergies. Some foods have been proven to be toxic to rats. Some of the foods rats are allergic to include.

  • Spoiled Produce. Spoiled or rotten produce can carry deadly bacteria and mold that produce toxins that could cause enough digestive distress to kill a rat.
  • Raw Sweet Potato. This unassuming vegetable contains some compounds that form cyanide when mixed with a rat’s stomach acid.
  • Green Potato. Green potatoes are particularly deadly to rats. Their bodies cannot effectively repel toxins in green potato eyes or skin.
  • Licorice. Research has found that licorice produces traumatic neurological effects in rats.
  • Insects. Insects can carry various parasites and diseases that could kill or seriously harm rats.
  • Raw/Dried Corn. Dried corn with high enough fungal contaminants can cause liver cancer in some rats.
  • Citrus Peels. D-limonene in citrus peels is known to cause kidney damage and could lead to kidney cancer, specifically in male rats.
  • Caffeine. Caffeine can increase a rat’s heart rate, cause cardiac malfunction and arrhythmia, and could cause a heart attack.
  • Blue Cheese. The main component that makes up blue cheese is mold. This mold is known to be toxic to rats.
  • Raw or Raw/Dried Beans. Natural or raw/dried beans contain hemagglutinin, which is highly toxic to rats because it destroys vitamin A and enzymes the rat needs to digest proteins and starches. Red blood cells clump up inside their circulatory system when a rat eats raw or raw/dried beans.
  • Green Bananas. Green bananas inhibit the enzymes found inside a rat’s digestive system to digest starches.
  • Alcohol. Alcohol is deadly to rats because it depresses the systems responsible for maintaining essential organs.

What Ingredients Do Instant Mashed Potatoes Contain?

Now that we have established what ingredients rats are allergic to let’s see if any identified items are found in instant mashed potato products. If the ingredients are what kills a rat, we expect to find at least one of these ingredients in the top 7 instant mashed potato brands.

If any of these products could be a suitable replacement for traditional rat poison, which one should you choose?

1. Idahoan Original Mashed Potatoes

  • Ingredients:
    • Idaho® Potato Flakes
    • Emulsifier (Monoglycerides)
    • Preservative (Sodium Acid Pyrophosphate, Sodium Bisulfite, Citric Acid, mixed tocopherols).
  • Gluten-free

2. Betty Crocker Real Mashed Potatoes Mix Pouches Butter & Herb

  • Ingredients:
    • Potatoes*
    • Salt
    • Maltodextrin
    • Butter (Cream, Salt)
    • Corn Syrup*
    • Spice
    • Buttermilk*
    • Parsley Flakes
    • Garlic*
    • Nonfat Milk
    • Natural and Artificial Flavor
    • Modified Corn Starch
    • Onion*
    • Partially Hydrogenated Soybean Oil
    • Silicon Dioxide (anticaking agent)
    • Color Added.
    • Emulsifier (Mono-and Diglycerides)
    • Preservatives (Sodium Acid Pyrophosphate, Sodium Bisulfite, Citric Acid)
  • *Dried.

3. Hungry Jack Potato Hungry Jack Mashed Potatoes

  • Ingredients:
    • Idaho® Potato Flakes
    • Monoglyceride
    • Preservatives (Sodium Acid Pyrophosphate, Sodium Bisulfite, Citric Acid, BHA)

4. Bob’s Red Mill Potato Flakes

  • Ingredients:
    • Dehydrated Potatoes

5. Idaho Spuds Classic Mashed Potatoes

  • Ingredients:
    • Preservatives (Sodium Acid Pyrophosphate, Sodium Bisulfite, BHA)
    • Sulfite ingredients
    • Milk ingredients

6. 365 Everyday Value Instant Mashed Potatoes

  • Ingredients:
    • Dehydrated potato
    • Butter (Cream Salt)
    • Salt
    • Nonfat milk
    • Natural flavor
    • Dehydrated garlic spices
    • Dehydrated onion
    • Rosemary extract

7. Ore Ida Homestyle Classic Simple’ N’ Creamy Mashed Potatoes

  • Ingredients:
    • Potatoes
    • Heavy Cream
    • Butter (Cream, Salt)
    • Salt

How Does Instant Mashed Potatoes Kill Rats?

As we can clearly see, the only real ingredient in instant mashed potatoes that could threaten a rat’s life is the small amount of modified corn starch found in Betty Crocker Real Mashed Potatoes Mix Pouches Butter & Herb. Even this amount probably won’t give a rat liver cancer, let alone kill it quickly enough before it can breed and take over your home.

Rats would hypothetically die from ingesting instant mashed potatoes, not the ingredients themselves but rather what happens when instant mashed potato flakes make contact with water or other fluids.

Research shows that potato flakes have a water absorption percentage between 8.57% and 10.48%. That means if a rat ingests dehydrated potato flakes, the rat’s stomach could expand up to 10%.

Because rats cannot regurgitate the food they have previously consumed, they will be unable to rid themselves of the now swollen mass inside their stomach. Suppose the rat’s stomach cannot digest the sizeable amount of instant mashed potato. In that case, it will have no room to ingest new nutritionally sufficient foods and starve to death.

Is Instant Mashed Potatoes More Effective Than Traditional Rat Poison?

Now that we know that it’s not the ingredients of instant mashed potato flakes that kill rats but rather how it interacts with water. Let’s compare it to more traditional rat poisons and see how the real “instant” killer is.

Traditional Rat Poison Ingredients And How They Kill Rats

There are four main active ingredients in the most common rat poisons. These ingredients are phosphides, bromethalin, cholecalciferol, and long-acting anticoagulants. Each one of these ingredients has its mechanisms for how they kill rats.

Let’s look at each ingredient individually to see how it attacks a rodent’s body.

1. Phosphides

Phosphides release a deadly gas produced in the rat’s stomach when the poison mixes with the rat’s stomach acid. The more food a rat has in its stomach, the more gas it produces. There is no antidote to this toxic substance. The only treatment is for a veterinarian to administer antacid medication to help decrease the amount of gas generated. This ingredient attacks the rat’s liver, lungs, and abdomen, causing pain, shock, bloating, nausea and seizures.

2. Bromethalin

Bromethalin, when ingested, causes the rat’s brain to start swelling. This poison does not cause bleeding and cannot be treated with vitamin K1. Common symptoms when this toxin is ingested before death include weakness, incoordination, seizure, paralysis, tremors, and lethargy.

3. Cholecalciferol

Cholecalciferol is most likely the most potent poison available. If this toxin is ingested in a large enough quantity (which isn’t as much as you might think), it will cause the amount of calcium in the blood to skyrocket. This increased blood calcium level will lead to kidney failure if left unattended.

The signs that this poison is active could take up to three days to appear long after it has already caused permanent damage to the rat’s body. Kidney failure usually develops two or three days after the rat has ingested this toxin.

4. Long-acting Anticoagulants

Long-acting anticoagulants, or LAACs, are the most common and recognizable type of rat poison. LAACs prevent the blood inside a rat’s body from clotting, resulting in internal bleeding. When a rat ingests this poison, it starts feeling lethargic. It has difficulty breathing (because its lungs are bleeding), gets fragile, and sometimes develops bruises on its body.

When instant mashed potato products are pitted against actual rat poisons, it is clear that it probably won’t be as effective as you might expect.

Pros And Cons Of Using Instant Mashed Potatoes Instead Of Rat Poison

What are several pros and cons of switching from traditional rat poison to instant mashed potato flakes?


  • Considerably cheaper than traditional Rat poison.
  • Safe to use when there are pets in the home.
  • Safe to use if there are small children in the home.
  • Easy to clean.
  • More humane than traditional rat poison.
  • Readily available at most retail outlets near you.
  • Less dangerous to handle than poison.
  • You can safely and efficiently spread it over a large area.
  • Very appealing smell to rats. Potato flakes make for good rat bait.
  • It has a long shelf life.
  • Once the rats are gone, you can use the flakes left in the box when cooking meals.


  • Potato flakes are less effective than traditional poison.
  • It can become cumbersome to clean if children or animals run through the area it is spread over.
  • Rats might not die quickly enough before they get a chance to reproduce.
  • It could be a waste of food and money if the rats don’t take a liking to it or if it fails to kill them.
  • Potato flakes’ efficacy in using rodent extermination does not have sufficient research to be called a proven method.

How To Use Potato Flakes As Rat Poison

If you want to try potato flakes as an alternative to more deadly traditional rat poisons, see the steps below to help you plan your extermination process.

Step 1

Ensure you buy enough potato flakes to cover a reasonably sized area where you suspect rats might gather, travel across, or nest.

Step 2

Fill a small bowl, low enough for a rat to reach, with potato flakes, and set it down on the ground at night. This little pile of food will further entice the rat with an ample food supply.

Step 3

Fill a small saucer with water and place it near the potato flakes. If the rat eats the potato flakes, it will most likely become very thirsty and will look for a source of fresh water. However, the water will surely do the trick if the rat’s stomach juices are insufficient to rehydrate the potato flakes.

Alternative Homemade Rat Poisons

If instant mashed potato flakes aren’t your thing and you are looking at using something in its place, consider the following options that are easy to make and have readily available ingredients.

1. Artificially Sweetened Peanut Butter

This homemade poison is arguably better at fending off mice than fighting a rat infestation, but it’s worth a shot if you aren’t planning on buying a box of poison.

Mix some peanut butter and artificial sweetener. About two small packets of sweetener will do the trick. Ensure the sweetener contains Aspartame (the key to making this poison work). Roll the peanut butter and sweetener mix into small balls, about the size of a pearl, and leave them around areas you suspect any rat would frequent.

2. Baking Soda

You probably already have a small tub of baking soda in your kitchen. So why not use that instead of going to the shops to buy poison? All you have to do is combine a teaspoon of baking soda into some filler food that a rat wouldn’t mind eating.

Like the peanut butter, mix your baking soda in, roll your tiny balls, and place them around the house. Alternatively, you could incorporate a small amount of flour, sugar, and baking soda in a shallow lid and put it near a wall you know the rat passes frequently.

3. Vitamin D

Crushing a small vitamin D tablet into a fine powder and leaving it out for a rat to find will have the same effects as cholecalciferol as it raises the amount of calcium in the rat’s bloodstream. Lucky for us, small doses of vitamin D are not poisonous to us, our kids, or our pets.


It might seem like complete nonsense, but instant mashed potatoes could work as an alternative to more traditional poisons. In the end, the results speak for themselves. For example, suppose you successfully used instant mashed potatoes to rid your home of a rodent infestation. In that case, you can feel proud of yourself for doing so more humanely instead of hiring an exterminator to terminate them.

Do You Need Pest Control Service?

Get FREE quotes from licensed pest control technicians in your area today. Whether you need spraying for ants, roaches, spiders, ticks, mosquitos, or bed bugs, We Can Help! All technicians are screened, licensed, and insured.

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Hubert Miles | Licensed Home Inspector, CMI, CPI

Hubert Miles is a licensed home inspector (RBI# 2556) with more than two decades of experience in inspection and construction. Since 2008, he has been serving South Carolina through his company, Patriot Home Inspections LLC. As a Certified Master Inspector, Hubert is dedicated to providing his expertise in home inspections, repairs, maintenance, and DIY projects.