15 Things You Should Never Put in the Microwave

Styrofoam, Travel Mugs, and Even Certain Foods

Plastic container and microwave

 BRETT STEVENS/ Cultura/ Getty Images

Microwave ovens have been a part of many American households since the mid-1970s and most users quickly learned to keep items such as aluminum foil and metal utensils out of this appliance. The burst of sparks was an easy clue, and the ensuing fire and ruined microwave were the final answers. But there remains a list of what you should not put in the microwave and it's for your own safety.

Cooking fires are the leading cause of reported house fires. According to a recent report from the National Fire Protection Association (NFPA), between 2014 and 2018, firefighters responded to an annual average of 172,900 home structure fires started by cooking activities. The NFPA says these fires caused an annual average of the following deaths, injuries, and damages:

  • 550 civilian deaths
  • 4,820 reported civilian fire injuries
  • More than $1 billion in direct property damage per year

For the preservation of your microwave and more importantly the health of your family, here are 15 things (in addition to metal that can't go in the microwave) that should never be placed in the microwave.

  • 01 of 15

    Styrofoam Cups and Containers

    While polystyrene foam or Styrofoam containers do a good job in protecting foods in the refrigerator, most foam containers aren't made for the microwave. Microwaving this type of foam can cause the carcinogenic substance styrene to seep into your food. The high heat can cause the container to break, dispersing hot food that can cause burns. Transfer the food to a microwave-safe container before heating.

  • 02 of 15

    Paper Bags and Takeout Containers

    Unless the paper bag is developed for use in the microwave, like popcorn bags, it is not safe to use for reheating. Brown paper lunch bags and printed paper takeout containers can release toxins into foods and can easily catch fire if the food becomes too hot. And don't forget that those paper Chinese food containers often have a thin metal wire handle that can create sparks and flames to ruin your microwave. If you're confused or questioning whether the container you have is microwave safe, don't put it in the microwave.

  • 03 of 15

    Lightweight Plastic Bags and Containers

    Keep grocery bags and any other lightweight plastic bags out of the microwave. They will melt! The same rule should be followed for margarine, yogurt, and cottage cheese tubs that are meant only for cold storage and one-time use. It may seem earth-friendly to reuse them, but it's not worth the risk of the chemicals released into your food during heating or a fire caused by the container melting.

    Many plastic containers contain bisphenol A or BPA, a chemical that has been linked to numerous health issues from cancer to diabetes. Heating the plastic releases the BPA into the food. Take the time to check that any plastic storage container is labeled as microwave-safe before hitting those buttons.

  • 04 of 15

    Travel Mugs

    If your coffee needs to be warmed up, use a glass or porcelain mug to heat it in the microwave before you pour it into a travel mug. Most travel mugs, cups, and bottles are made of plastic or stainless steel. You know that metal is a no-no for the microwave, and it will prevent the beverage from being heated. Plastic mugs may not be safe and can even separate and ruin the insulation that keeps the beverage hot.

    Continue to 5 of 15 below.
  • 05 of 15

    Vintage Plates and Cups

    If you have some vintage Fiestaware or any dishware that is more than 40 years old, don't use them in the microwave. The glaze could contain lead or other components that could leach into food when heated to high temperatures. Any gold or silver-gilded dishes should also be avoided.

  • 06 of 15

    Uncovered Containers

    Unless you like cleaning the microwave, make sure that every container is covered. A vented microwave cover will make your life much easier. For example, if you put any type of container with any type of sauce (such as tomato) in the microwave without a cover, you can be sure the contents will explode in the microwave from becoming rapidly overheated.

  • 07 of 15

    Fabrics and Clothes

    This may seem out of place, but there are "hacks" floating around the internet that you can dry fabrics in the microwave. Never put any type of linens or clothing in the microwave. Your damp shoes will never be the same.

  • 08 of 15

    Hot Peppers

    Unless you like the effects of pepper spray, avoid placing chili peppers in the microwave. The heat releases the capsaicin in the peppers and causes it to vaporize, burning your eyes, nose, and lungs.

    Continue to 9 of 15 below.
  • 09 of 15

    Egg in a Shell

    As the egg heats, all that steam has nowhere to go in the shell until it builds to the point where the egg explodes—even if you place it in a dish with water. If you're making an egg in a mug recipe, you've hopefully cracked the egg out of its shell and beat it a bit, so it's safer to microwave without making much of a mess or explosion.

  • 10 of 15

    Whole Fruits

    Placing grapes, whole peachesapples, or pears in a microwave can cause an explosion when the steam builds up inside the skin or create a serious scald when you try to open the steaming hot fruit.

  • 11 of 15

    Frozen Meats

    One of the benefits of the microwave is the quick, intense heat to thaw and cook frozen foods. One of the foods that should be monitored carefully is frozen meat. Because the meat is usually thick—especially ground beef—it is difficult to ensure that the center is fully-cooked. This can result in over-cooked areas while some spots are still raw.

  • 12 of 15

    Frozen Breast Milk

    Breast milk should be thawed in the refrigerator instead of the microwave. Uneven heating is dangerous and can scald the baby's throat.

    Continue to 13 of 15 below.
  • 13 of 15

    Nothing at All

    Never turn on the microwave when it is empty. When the microwaves have no destination like liquids or food, they bounce off each other and are reabsorbed into the microwave, which can cause it to explode and start a potentially deadly fire.

  • 14 of 15

    Leafy Greens

    Leafy greens such as kale, raw carrots, and fresh spinach, and sometimes processed meats such as hot dogs, can cause sparking and arcing in the microwave while cooking. The likely reason is metallic trace minerals in the food are reacting to the microwaves. The food may not heat up evenly, but more important, arcing can damage your microwave oven. If you see arcing (sparking), stop the oven and remove the item immediately to avoid damage to your microwave.

  • 15 of 15

    Cup of Water

    Boiling a cup of water in the microwave seems quick and easy. But, if you overdo it, the cup and the water can be extremely hot, causing scalding and minor burns, or it could explode (rare) while in the microwave. Though it can take a minute or so longer, it's safest to boil water the old-fashioned way in a pot or kettle on the stove.


    Can you put glass in the microwave? To be on the safe side, only put glass in your microwave if it is labeled as "microwavable safe." If it has that label, it is designed to withstand the high temperatures of a microwave oven. Other types of glass may shatter if microwaved.

Article Sources
The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Cooking Fires Public Education. National Fire Protection Association.

  2. Home Cooking Fires, News & Research. National Fire Protection Association.

  3. Styrene. United States Department of Health and Human Services.

  4. Use only microwave safe containers when cooking and reheating foods. Michigan State University.

  5. Provvisiero DP, Pivonello C, Muscogiuri G, et al. Influence of Bisphenol A on Type 2 Diabetes MellitusInt J Environ Res Public Health, vol. 13, no. 10, pp. 989. 2016. doi:10.3390/ijerph13100989

  6. Lead Contamination of Food. Extonet, Oregon State University.

  7. Fattori V, Hohmann MS, Rossaneis AC, Pinho-Ribeiro FA, Verri WA. Capsaicin: Current Understanding of Its Mechanisms and Therapy of Pain and Other Pre-Clinical and Clinical Uses. Molecules, vol. 21, no. 7, pp. 844, 2016. doi:10.3390/molecules21070844

  8. Heating Human Milk. La Leche League International.

  9. Cooking With Microwave Ovens: What is Arcing? USDA Food Safety and Inspection Service.

  10. Risk of Burns from Eruptions of Hot Water Overheated in Microwave Ovens. U.S. Food and Drug Administration.