Styrofoam, Travel Mugs, and Even Certain Foods
Mary Marlowe Leverette
Mary Marlowe Leverette
Mary Marlowe Leverette is one of the industry's most highly-regarded housekeeping and fabric care experts, sharing her knowledge on efficient housekeeping, laundry, and textile conservation. She is also a Master Gardener with over 40 years' experience; writing for over 20 years.
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Updated on 10/02/22
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Fact checked bySarah Scott
Sarah Scott is a fact-checker and researcher who has worked in the custom home building industry in sales, marketing, and design.
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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
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 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.(Video) 8 Things You Should Never Put In The Microwave
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
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
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 theeggheats, 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(Video) 3 Things You Should Never Put In The Microwave - (Don't Do It!)
Placinggrapes, wholepeaches,apples, or pearsin a microwave can cause an explosion when the steam builds up inside the skin or create a serious burn when you try to open the steaming hot fruit.
11 of 15
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 isfrozen 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 milkshould be thawed in the refrigerator instead of the microwave. Uneven heating is dangerous and can burn 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 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.
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.
Cooking Fires Public Education. National Fire Protection Association.
Home Cooking Fires, News & Research. National Fire Protection Association.
Styrene. Agency for Toxic Substances and Disease Registry, Division of Toxicology and Human Health Sciences.
Can You Microwave Styrofoam? Medical News Today.
Kitchen Safety: Some Recycled Containers Are Not Food Safe. University of Illinois College of Agriculture, Consumer & Environmental Sciences.
Provvisiero DP, Pivonello C, Muscogiuri G, et al. Influence of Bisphenol A on Type 2 Diabetes Mellitus.Int J Environ Res Public Health. 2016;13(10):989. doi:10.3390/ijerph13100989
Heating Human Milk.La Leche League International.
Why Do Veggies Spark in the Microwave? Children's Museum Indianapolis.
Cooking With Microwave Ovens: What is Arcing? USDA Food Safety and Inspection Service.
Risk of Burns from Eruptions of Hot Water Overheated in Microwave Ovens. U.S. Food and Drug Administration.
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- Rice. Rice contains spores of Bacillus cereus, a bacterium that can cause food poisoning. ...
- Coffee. ...
- Hard-boiled eggs. ...
- Fish. ...
- Turkey. ...
- Foods you've already reheated.
Metal twist ties: may cause arcing and could cause a fire in the oven. Paper bags: may cause a fire in the oven. Plastic foam: plastic foam may melt or contaminate the liquid inside when exposed to high temperature.Can you microwave an egg? ›
Yes, it is safe to cook eggs in the microwave, whether you wish to poach, scramble, or “fry” your eggs. Sometimes, microwaved eggs taste even better than stovetop eggs. For example, you can make perfectly poached eggs in the microwave without needing to form a whirlpool. More on that in a bit.What happens if you microwave honey? ›
Don't microwave raw honey to decrystallize it. Microwave ovens cook food unevenly (that is why you have to turn your microwave dinner halfway through the cycle). You can't control the temperature at all and are likely to scorch or boil at least some of your raw honey in a microwave.Is it safe to microwave a potato? ›
It is completely safe to cook potatoes in the microwave, as long as you remember to prick the potatoes beforehand. By pricking the skin you avoid a messy, hot potato explosion in your microwave. Microwaving lowers the time of cooking, you can cook the potatoes in 5 minutes instead of 20 minutes.What happens if u put milk in the microwave? ›
What happens if you microwave milk? When milk is microwaved, the electromagnetic radiation excites the water molecules in the liquid, thereby creating vibration that results in heat energy. As the water molecules become for energetic, more heat is generated causing the milk to heat up.What food can't you reheat? ›
There aren't necessarily any cooked foods that you should not reheat. However, we do recommend that you are particularly cautious when reheating meat, seafood or rice. If you cool, store, and then reheat these foods properly, they should be safe to eat without the risk of food poisoning.Can you microwave a hard boiled egg? ›
Weirdly enough, reheating a hard boiled egg in a microwave is a hazard, and it can potentially explode. Hard boiled eggs explode in the microwave because a boiled egg still has moisture inside, allowing steam to build up in the yolk.Why do ramen noodles say do not microwave? ›
Cup of Noodles usually comes in a Styrofoam container. Adding the water and then heating it in the microwave could cause the Styrofoam to melt from the heat of the water.Is it safe to put aluminum foil in microwave? ›
The FDA reiterates that food completely covered in aluminum foil should not be put in the microwave here . The electric fields in microwaves cause charges to flow through metal. Thin pieces of metal like aluminum foil are overwhelmed by these currents, causing them to heat up so quickly that they can ignite.
Yes, as long as the glassware is labeled “microwave safe.” This means the glass is designed to handle high temperatures. In most cases, plastic to-go containers aren't microwaveable, nor are styrofoam containers, so reheating takeout is safest in a glass dish.Can you boil water in a microwave? ›
Can I use my microwave to boil water? Yes, water can be boiled in a microwave using a microwave-safe container. Use a wooden stick (like a chopstick or coffee stir stick) in your microwave safe container to prevent superheated water.Can I cook bacon in microwave? ›
In general it takes between 3 and 6 minutes to cook bacon in the microwave. This could vary depending on your microwave's wattage, how thick your bacon is, the type of bacon (turkey bacon will have a shorter cooking time), how much bacon you're cooking, and how crispy you want it to be.What foods should not be reheated? ›
- Vegetables with High Amounts of Nitrates. ...
- Rice. ...
- Eggs. ...
- Chicken. ...
- Potatoes. ...
- Mushroom. ...
- Cold Pressed Oil.
Substantial pieces of metal, like the walls of a microwave oven, can usually tolerate these currents without any problems. However, thin pieces of metal, like aluminum foil, are overwhelmed by these currents and heat up very quickly. So quickly in fact, that they can cause a fire.What happens if you put aluminum foil in the microwave? ›
The electric fields in microwaves cause charges to flow through metal. Thin pieces of metal like aluminum foil are overwhelmed by these currents, causing them to heat up so quickly that they can ignite.Is it bad to heat Styrofoam in the microwave? ›
Because styrene has been linked to cancer, microwaving Styrofoam can be unsafe. The compound and other harmful chemicals may leak into food since the containers can melt or break down at high temperatures when microwaved, according to Mr.Appliance.com.