Chemicals You Should Never Mix

Household Chemicals That Don't Belong Together

Some common household chemicals should never be mixed. They may react to produce a toxic or deadly compound or they may cause undesirable consequences. Here's what you need to know.

Key Takeaways: Chemicals You Shouldn't Mix

  • Common household chemicals--even ones used in cooking--may pose risks if they are mixed with other chemicals.
  • Always read and heed warnings on product labels. In addition to avoiding mixing chemicals, some chemicals should be stored separately from one another.
  • In particular, don't mix bleach or peroxide with other chemicals unless product instructions specifically instruct you to do so. Never mix cleaning products not intended to work together.
  • Play it safe instead of playing mad scientist. Chemicals make our lives easier, but they should be treated with caution and respect.
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Bleach + Ammonia = Toxic Chloramine Vapor

Safe chemicals can react to produce dangerous ones.
Doug Armand, Getty Images

Bleach and ammonia are two common household cleaners that should never be mixed. They react together to form toxic chloramine vapors and may lead to the production of poisonous hydrazine.

What It Does: Chloramine burns your eyes and respiratory system and can lead to internal organ damage. If there is enough ammonia in the mixture, hydrazine may be produced. Hydrazine is not only toxic but also potentially explosive. The best-case scenario is discomfort; the worst-case scenario is death.

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Bleach + Rubbing Alcohol = Toxic Chloroform

Chloroform is also known as trichloromethane (TCM) and methyl trichloride.
Ben Mills

The sodium hypochlorite in household bleach reacts with ethanol or isopropanol in rubbing alcohol to produce chloroform. Other nasty compounds that may be produced include chloroacetone, dichloroacetone, and hydrochloric acid.

What It Does: Breathing enough chloroform will knock you out, which will make you unable to move to fresh air. Breathing too much can kill you. Hydrochloric acid can give you a chemical burn. The chemicals can cause organ damage and lead to cancer and other diseases later in life.

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Bleach + Vinegar = Toxic Chlorine Gas

Chlorine gas is an irritant and it's toxic.
Pamela Moore, Getty Images

Are you noticing a common theme here? Bleach is a highly reactive chemical that should not be mixed with other cleaners. Some people mix bleach and vinegar to increase the cleaning power of the chemicals. It's not a good idea because the reaction produces chlorine gas. The reaction isn't limited to vinegar (weak acetic acid). Avoid mixing other household acids with bleach, such as lemon juice or some toilet bowl cleaners.

What It Does: Chlorine gas has been used as a chemical warfare agent, so it's not something you want to be producing and inhaling in your home. Chlorine attacks the skin, mucous membranes, and respiratory system. As best, it will make you cough and irritate your eyes, nose, and mouth. It can give you a chemical burn and could be deadly if you are exposed to a high concentration or are unable to get to fresh air.

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Vinegar + Peroxide = Peracetic Acid

Paracetic acid is corrosive.
Johannes Raitio, stock.xchng

You might be tempted to mix chemicals to make a more powerful product, but cleaning products are the worst choice for playing home chemist! Vinegar (weak acetic acid) combines with hydrogen peroxide to produce peracetic acid. The resulting chemical is a more potent disinfectant, but it's also corrosive, so you turn relatively safe household chemicals into a dangerous one.

What It Does: Peracetic acid can irritate your eyes and nose and may give you a chemical burn. ​

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Peroxide + Henna Hair Dye = Hair Nightmare

Henna is a common red hair dye for home coloring.
Laure LIDJI, Getty Images

This nasty chemical reaction is most likely to be encountered if you color your hair at home. Chemical hair dye packages warn you not to use the product if you have colored your hair using a henna hair dye. Similarly, henna hair coloring warns you against using a commercial dye. Why the warning? Henna products other than red contain metallic salts, not just ground-up plant matter. The metal reacts with hydrogen peroxide in other hair colors in an exothermic reaction that can cause a skin reaction, burn you, make your hair fall out, and produce a scary unpredictable color in hair that remains.

What It Does: Peroxide removes existing color from your hair, so it's easier to add a new color. When it reacts with metal salts (not ordinarily found in hair), it oxidizes them. This ruins the pigment from the henna dye and does a number on your hair. Best case scenario? Dry, damaged, weird-colored hair. Worst case scenario? Welcome to the wonderful wide world of wigs.

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Baking Soda + Vinegar = Mostly Water

Baking soda and vinegar mix for volcanoes, not cleaning.

While the previous chemicals on the list combined to produce a toxic product, mixing baking soda and vinegar gives you an ineffective one. Oh, the combination is fantastic if you want to produce carbon dioxide gas for a chemical volcano, but negates your efforts if you intend to use the chemicals for cleaning.

What It Does: Baking soda (sodium bicarbonate) reacts with vinegar (weak acetic acid) to produce carbon dioxide gas, sodium acetate, and mostly water. It's a worthwhile reaction if you want to make hot ice. Unless you are mixing the chemicals for a science project, don't bother.

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AHA/Glycolic Acid + Retinol = Waste of $$$

Anti-aging products are expensive, so don't waste the investment inactivating them by accident.
Dimitri Otis, Getty Images

Skincare products that actually work to lessen the appearance of fine lines and wrinkles include alpha-hydroxy acids (AHAs), glycolic acid, and retinol. Layering these products won't make you wrinkle-free. In fact, the acids reduce the effectiveness of retinol.

What It Does: Skincare products work best at a certain acidity level or pH range. When you mix products, you can change the pH, making your expensive skin care regimen pointless. Best case scenario? The AHA and glycolic acid loosen dead skin, but you get no bang for your buck from the retinol. Worst case scenario? You get added skin irritation and sensitivity, plus you wasted money.

You can use the two sets of products, but you need to allow time for one to be completely absorbed before applying the other. Another option is to alternate which type you use.

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Your Citation
Helmenstine, Anne Marie, Ph.D. "Chemicals You Should Never Mix." ThoughtCo, Apr. 5, 2023, Helmenstine, Anne Marie, Ph.D. (2023, April 5). Chemicals You Should Never Mix. Retrieved from Helmenstine, Anne Marie, Ph.D. "Chemicals You Should Never Mix." ThoughtCo. (accessed May 29, 2023).