10 Things You Should Never Put in the Microwave

Microwaves have revolutionized the way we cook, making it easier and faster to heat our meals.

Despite the convenience, it’s important to remember that not everything is suitable for microwave use. 

Knowing what goes into your microwave can help you maintain a safe cooking experience. It will also help to prolong the microwave’s lifespan.

Allow me to share with you ten things you should never put in your microwave. Let us begin.

Things You Should Never Put in the Microwave

Here are ten things you should never put in your microwave: 

Item Not to MicrowaveReason Not to Microwave
Frozen MeatCauses uneven cooking and increases the risk of foodborne illness due to bacteria growth. Can make meat tough and chewy.
Hard-Boiled EggsSteam pressure inside can build up, causing the egg to explode, potentially causing injury and mess.
Breast MilkUneven heating can result in hot spots that can burn a baby’s mouth and throat. Microwaving can destroy essential nutrients.
Chinese Take-Out ContainersSome may have a metal rim or plastic lining, posing a risk when microwaved.
Plastic ContainersCertain plastics release harmful chemicals like BPA when heated. Check for microwave safety and BPA-free labels.
Styrofoam ContainersCan cause carcinogenic styrene to seep into food and may break down at high temperatures, causing burns and health risks.
Metallic Trimmed PlatesThe metal trim can cause sparks and a potential fire hazard in the microwave.
Stainless Steel Travel MugsMetal in the microwave can cause sparks and fire hazards. Metal handles have the same risks.
Chili PeppersMicrowaving can release capsaicin into the air, causing irritation, and uneven heating can lead to overcooking or exploding.
GrapesCan lead to the formation of superheated plasma, damaging the microwave or causing a fire hazard.
Paper BagsCan release toxins and catch fire; not designed for microwave use like popcorn bags. Increases the risk of fire and contamination.

Frozen Meat

Heating frozen meat in a microwave oven can result in uneven cooking, leaving some parts cooked while others remain cold. 

This can make it difficult to determine the correct cooking time, increasing the risk of foodborne illness due to bacteria growth. 

Microwaves can also cause proteins in the meat to become tough and chewy, altering the texture and taste.

How to Heat Instead

To properly defrost frozen meat, it is best to place it in the refrigerator and allow it to thaw gradually

This method keeps the meat within a safe temperature range, minimizing the risk of bacteria growth. 

Plan, as this can take several hours or even days, depending on the size and thickness of the meat.

If you’re in a hurry, submerge the sealed meat in cold water, changing the water every 30 minutes. This method is faster than refrigerator thawing but still maintains a safe temperature. 

For quicker thawing, use the defrost setting on your microwave oven. Although not ideal, it is safer than using regular heating. Once defrosted, cook the meat immediately to ensure its safety.

Remember to avoid using high heat settings when defrosting meat in a microwave. 

Instead, opt for a lower power or the designated defrost setting. Keep an eye on the progress, pausing occasionally to break apart or rearrange the meat for more even thawing.

Also read: Does Air Fryer Dry Out Food (Meat/Chicken)?

Hard-Boiled Eggs

Microwaving hard-boiled eggs is not recommended, as the steam pressure within the egg white can build up and cause it to explode. 

This can be dangerous, making a mess in your microwave, and potentially causing injury. To avoid these risks, it is best to find alternative ways to heat your hard-boiled eggs.

How to Heat Instead

If you want to enjoy a hard-boiled egg, there are several other methods to heat it without using a microwave. 

A simple approach is to place the egg in a bowl of hot water for a few minutes on the stovetop. Be sure to use tongs or a slotted spoon to remove the egg to avoid burns.

Another option is to reheat the egg gently on the stove using a double boiler or a heat-proof bowl set over a saucepan with simmering water. 

With this method, your egg will heat evenly without being exposed to direct heat.

Regardless of the method you choose, it is crucial to handle the eggs carefully to avoid burns and ensure even heating. 

Also read: Can You Cook Eggs in the Microwave?

Breast Milk

Heating breast milk in a microwave is not recommended due to uneven heating that can result in hot spots, which can cause burns to a baby’s mouth and throat. 

Microwaving can also destroy the essential nutrients present in breast milk, thus compromising its nutritional value for your baby.

How to Heat Instead

To ensure food safety for your baby, it is crucial to apply alternative methods when heating breast milk. Here are some safe ways to warm breast milk:

Warm Water Bath

Place the breast milk container in a bowl of warm water. Gently swirl the container to distribute the heat evenly. Keep the water warm but not hot to prevent overheating the milk.

Bottle Warmer

A designated bottle warmer is a safe and convenient option for warming breast milk bottles. Make sure to follow the manufacturer’s instructions for the particular model you own.

Under Running Water

Hold the container of breast milk under warm running water, rotating it gently to ensure even heating. Make sure that the water doesn’t enter the milk container.

It is essential to always test the temperature of the breast milk before feeding it to your baby. 

The milk should feel lukewarm, not hot. Avoid refreezing thawed breast milk, as this jeopardizes the quality and safety of the milk and may encourage harmful bacteria growth.

Also read: Can You Heat Almond Milk?

Chinese Take-Out Containers

It is important to know that not all take-out containers are safe to be used in the microwave. 

Some Chinese take-out containers may have a metal rim or be lined with plastic materials, which could pose risks when microwaving.

How to Heat Instead

To safely reheat food in your Chinese take-out, it’s best to transfer it into a microwave-safe container. 

Here are some alternative methods to heat your leftovers:

Microwave-Safe Container

First, transfer your food to a microwave-safe container made of glass or ceramic. Cover it with a microwave-safe lid or plastic wrap, leaving a small opening for steam to escape. 

Heat the food at 50% power for 1-2 minutes, stirring occasionally to ensure even cooking.


Preheat your oven to 350°F (175°C). Transfer the leftovers to an oven-safe dish, cover it with aluminum foil, and heat for about 10-15 minutes, or until the food is heated thoroughly. 

Check the temperature with a food thermometer to ensure it reaches at least 165°F (74°C) as recommended by the USDA.


For stir-fry dishes, use a large skillet or wok. Heat a small amount of oil over medium heat. Add the leftovers and cook, stirring continuously for a few minutes until the food is heated through.

Plastic Containers

When using the microwave, it’s important to know which plastic containers are safe for heating food. 

Some plastics release harmful chemicals, like BPA and other toxic substances, when exposed to high temperatures. 

To avoid these risks, always use microwave-safe containers that are specifically labeled as BPA-free.

Not all plastic is created equal, and it’s important to know what types should not be put in the microwave. 

For example, plastic bags and yogurt tubs are generally not considered microwave-safe, as they may contain BPA and can easily melt or warp under high heat.

Here is a quick list of plastic types and their microwave safety:

Plastic TypeMicrowave Safe?
PET or PETE (#1)No
HDPE (#2)Yes
PVC or V (#3)No
LDPE (#4)Yes
PP or P(#5)Yes
PS (#6)No
Other (#7)No

How to Heat Instead

If you don’t have a microwave-safe, BPA-free plastic container, there are alternative methods for heating food. Here are a few suggestions:


Use an oven-safe glass or ceramic container for a consistent and even heat distribution. Be sure to adjust cooking time and temperature accordingly.


Transfer food to a pot or pan and heat it on the stovetop. This is especially effective for reheating soups, sauces, or other liquid-based meals.

Toaster Oven

Smaller than a traditional oven, a toaster oven can reheat food quickly and evenly, with lower energy consumption.

Also read: Air Fryer Smells Like Plastic – How to Get Rid of the Smell?

Styrofoam Containers

Styrofoam containers, made of polystyrene foam, are commonly used for takeout food and as disposable cups and plates. 

These lightweight containers are convenient, but they should never be placed in a microwave. 

Microwaving Styrofoam can cause the carcinogenic substance styrene to seep into your food, posing a risk to your health. 

Additionally, the high heat can cause the container to break, dispersing hot food that can cause burns.

How to Heat Instead

Transfer your food to a microwave-safe dish before heating. 

Avoid using aluminum foil or metal containers, as they can damage the microwave. Glass, ceramic, and some plastic containers specifically designed for microwaving are safe options.

Metallic Trimmed Plates

It’s important to be aware that metallic trimmed plates should never be placed in a microwave. The metal trim on these plates can cause sparks, leading to a potential fire hazard. 

When microwaving food, always choose microwave-safe plates without any metallic trim.

How to Heat Instead

Here are some alternative methods to heat the food in your metallic trimmed plates:


Transfer your food to a non-metallic, heat-safe plate or container and heat it on the stovetop using low to medium heat.


You can place your food in an oven-safe dish and heat it in a preheated oven at a low temperature.

Toaster Oven

Another option is to use a toaster oven, which can be a more energy-efficient alternative to a full-size oven.

Also read: Can You Microwave Aluminum Takeout Containers?

Stainless Steel Travel Mugs

One of the items you should never put in the microwave is stainless steel travel mugs. Stainless steel is a type of metal, and microwaves and metals are not a good mix. 

When you place a stainless steel travel mug in the microwave, it can cause sparks and even start a fire due to the way microwaves work with metal objects. 

Additionally, metal handles found on some mugs can have the same hazardous effect.

How to Heat Instead

To avoid damaging your microwave or causing a fire, you can follow a few alternatives to heat your beverage in a stainless steel travel mug. 

Firstly, you can simply pour the contents of your travel mug into a microwave-safe container (like a ceramic or glass mug), and then microwave it. 

After the contents are heated, simply pour it back into your travel mug.

Another option is to heat a separate mug of water in the microwave. 

Once heated, steep your stainless steel travel mug in hot water for some minutes, allowing the heat to transfer to the contents of your travel mug. 

This method can take a bit longer but can be a safer option for heating your beverage.

Also read: Hydro Flask Mug vs. Yeti Mug

Chilli Peppers

Heating chili peppers in the microwave is not recommended due to the presence of capsaicin, the compound that determines their spiciness. 

When microwaved, chili peppers can release capsaicin into the air, causing a burning sensation in your eyes and throat. 

Additionally, the uneven heating of a microwave can result in overcooked or exploded peppers, ruining both your meal and your cookware.

It is crucial to choose the right cooking method for your hot peppers. Try alternative ways to heat these fiery fruits to preserve their flavor, color, and texture.

How to Heat Instead

Consider these safer and more effective methods for heating chili peppers:

Stovetop Cooking

Sauté or stir-fry your chili peppers in a pan with a bit of oil. This method allows you to control the heat and avoid uneven cooking.

Oven Roasting

Place chili peppers on a baking sheet and roast them in the oven at a moderate temperature. Check them regularly to avoid overcooking or burning. Roasting enhances the peppers’ natural flavors and caramelizes their sugars, adding depth to their taste.


For an outdoor option, grill the chili peppers over direct heat, turning frequently for even cooking. Grilling imparts a smoky flavor that complements the peppers’ natural heat.

When handling chili peppers, wear gloves and avoid touching your eyes or face. The capsaicin can cause irritation and burning sensations.

Also read: Why is My Microwave Leaking Brown Liquid?


One surprising item that should never be microwaved is grapes. Microwaving grapes can lead to the formation of superheated plasma and damage your appliance or pose a fire hazard. 

This unusual phenomenon occurs due to the unique characteristics of grape skin combined with the electromagnetic fields generated in the microwave oven.

When grapes are exposed to microwave radiation, the energy is absorbed, and voltage differences can develop between the two ends of the grape. 

This creates a spark that jumps between the grape halves, leading to the formation of plasma

Plasma is a superheated gas that emits a bright light and can severely damage your microwave or cause a fire if left unchecked.

Note that this doesn’t only happen with grapes but can also occur with other fruits containing a high amount of water and sugar. 

Berries, such as blueberries and blackberries, can pose similar risks when microwaved.

How to Heat Instead

To safely heat grapes or other delicate fruits, it’s best to use alternative methods. Here are a few options:


You can gently warm grapes in a saucepan over low heat. Be sure to stir them occasionally to distribute the heat evenly and prevent burning.


Preheat your oven to a low temperature (around 200°F) and place the grapes on a baking sheet lined with parchment paper

Bake the grapes for a few minutes, checking them frequently to ensure they don’t overheat or burn.


Place the grapes in a steamer basket over a pot of simmering water. Cover and steam the grapes for a couple of minutes, until they’re warmed through.

Paper Bags

Using paper bags in the microwave can be dangerous, as they can release toxins and even catch fire if not meant for microwave use. 

It may be tempting to heat your lunch or leftovers in a paper bag, but it’s important to know the risks involved. 

Regular paper bags, like those used for lunch or groceries, don’t have the same features as microwave popcorn bags. 

Microwave popcorn bags contain susceptors, which are designed to absorb microwaves and keep the bag safe, while regular paper bags do not have this feature.

Microwaving paper bags can cause steam to build up inside the bag, leading to an increased risk of fire. 

Even if the bag doesn’t catch fire, the steam can make the bag soggy and unstable, which might cause spills or burns. 

Furthermore, heating paper bags in the microwave can cause the release of toxins, which could contaminate your food and potentially harm your health.

How to Heat Instead

If you need to heat something in the microwave, it’s best to transfer the food from the paper bag to a microwave-safe container or use a kitchen sponge for more delicate items.

When selecting a container, make sure it’s marked as microwave-safe or specifically designed for microwave use. 

Materials like glass, ceramic, and certain types of plastic are generally safe for microwave use. 

By using the appropriate container, you can enjoy a hot meal without the risks associated with microwaving paper bags.

In addition to choosing the right container for your food, you should also consider using microwave-safe covers or lids to prevent splatters and contain steam. 

This will not only keep your microwave clean but also help retain moisture, ensuring that your food heats evenly and stays delicious.

Also read: Can You Put Parchment Paper in Microwave?

Frequently Asked Questions

Here are some frequently asked questions you may find helpful. 

Why Is It Dangerous to Put Metal Objects in the Microwave?

Microwaving metal objects can cause a fire hazard and damage your microwave. 

Metals such as aluminum foil, utensils, or metal containers can create electric currents, causing arcing (sparks), and ignite any flammable materials inside the oven. 

Avoid using metal objects when microwaving food.

Which Types of Plastics Should Be Avoided in the Microwave?

Certain plastics may contain chemicals like BPA that can leach into your food when heated in a microwave. 

Not all plastics are microwave-safe, so it’s crucial to look for plastics labeled as “microwave-safe” or check the manufacturer’s instructions. 

Avoid heating food in single-use plastic containers, plastic wrap, or plastic bags that aren’t explicitly designed for microwave use.

What Risks Are Involved With Microwaving Styrofoam Containers?

Heating Styrofoam containers in the microwave may pose potential health risks. 

Styrofoam can release harmful chemicals, such as styrene when exposed to high temperatures. 

These chemicals can leach into your food and cause adverse health effects. It’s better to transfer your food to a microwave-safe dish before heating it to avoid any risks.

Are There Certain Foods That Are Unsafe to Heat in the Microwave?

Some foods can become unsafe or dangerous when microwaved. 

For example, leafy greens, raw carrots, and grapes can cause sparking and arcing in the microwave due to metallic trace minerals reacting to microwaves. 

Additionally, eggs in their shells and sealed containers can explode from steam pressure buildup if microwaved.

How Can You Identify Dishes That Are Not Safe for Microwave Use?

To determine if a dish is microwave-safe, check the bottom or sides for microwave-safe labels or symbols. If you’re unsure, perform the “water test.” 

Fill the dish with water, place it in the microwave, and heat it for one minute. If the dish becomes hot while the water remains cool, the dish is not microwave-safe.

What Happens if you accidentally microwave a grape?

Grapes can become superheated when microwaved, causing their sugary pulp to turn into molten plasma. 

This can lead to the grape exploding inside the microwave or even when you take a bite, potentially causing burns. To prevent accidents, always avoid microwaving grapes.

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I’m Jueria and I am a regular contributor on cookeryspace.com. In my articles, I share time-saving techniques, appliance wizardry, and health-friendly recipes to bring taste and wellness to your table. So raise a glass (or a spatula) with me, to good health and good food, made easy!