Discover the hidden dangers of reheating common leftovers—and how to enjoy them safely.
Microwaves are kitchen heroes: fast, convenient, and perfect for reviving last night’s dinner. But not all foods play nice with microwave reheating. Some lose flavor, others become rubbery, and a few can even pose serious health risks when zapped the wrong way.
If you’ve ever reheated rice only to feel queasy later—or turned a juicy steak into a chewy disappointment—you’re not alone. Here are 10 foods you should never reheat in the microwave, along with the science-backed reasons why—and safer alternatives to keep your meals delicious and safe.
1. Rice
Why it’s risky: Uncooked rice can contain Bacillus cereus, a bacteria that survives cooking. When rice is left at room temperature after cooking, the spores can multiply and produce toxins. Reheating in the microwave may not reach a high enough temperature to destroy these toxins, leading to food poisoning (symptoms: nausea, vomiting, diarrhea).
Safer alternative: Cool cooked rice quickly and refrigerate within 1 hour. Reheat thoroughly on the stovetop or in the oven until piping hot (165°F/74°C) throughout.
2. Chicken
Why it’s risky: Chicken must be reheated to at least 165°F (74°C) to kill harmful bacteria like Salmonella. Microwaves heat unevenly, leaving cold spots where bacteria can survive. Plus, reheating chicken multiple times breaks down proteins, making it dry and tough.
Safer alternative: Reheat shredded or diced chicken in a skillet with a splash of broth, or bake in the oven at 350°F (175°C) until steaming hot.
3. Mushrooms
Why it’s risky: Mushrooms are highly perishable. If not stored properly after cooking, their proteins degrade quickly. Reheating—especially in a microwave—can cause digestive upset due to changes in their protein structure.
Safer alternative: Eat cooked mushrooms cold in salads, or gently reheat them in a pan over low heat with a bit of oil or butter.
4. Eggs (Hard-Boiled or Scrambled)
Why it’s risky: Reheating eggs in the microwave can cause them to explode due to steam buildup inside the yolk. Even if they don’t burst, the texture turns rubbery and sulfurous odors intensify.
Safer alternative: Enjoy hard-boiled eggs cold. For scrambled eggs, reheat gently in a nonstick pan over low heat while stirring.
5. Leafy Greens (Spinach, Kale, Beet Greens)
Why it’s risky: These greens are high in nitrates. When reheated—especially multiple times—nitrates can convert to nitrites and potentially harmful nitrosamines, which are linked to health concerns.
Safer alternative: Cook only what you’ll eat fresh. If you must reheat, do so quickly on the stovetop and consume immediately.
6. Potatoes (Especially Baked)
Why it’s risky: Cooked potatoes left at room temperature can harbor Clostridium botulinum, the bacteria that causes botulism. Microwaving may not heat them evenly enough to kill spores.
Safer alternative: Store cooked potatoes in the fridge immediately. Reheat in the oven or air fryer to restore crispness and ensure even heating.
7. Fish
Why it’s risky: Fish reheated in the microwave often becomes dry, rubbery, and emits a strong, unpleasant odor. More importantly, uneven heating can leave cold zones where bacteria thrive.
Safer alternative: Flake leftover fish into salads or tacos. To reheat, steam gently or warm in a covered skillet with a splash of water or lemon juice.
8. Breast Milk or Baby Formula
Why it’s risky: Microwaves create hot spots that can scald a baby’s mouth—even if the bottle feels cool on the outside. Microwaving also destroys some immune-boosting properties in breast milk.
Safer alternative: Warm bottles by placing them in a bowl of warm water or using a dedicated bottle warmer. Always shake well and test temperature before feeding.
9. Processed Meats (Hot Dogs, Deli Meats)
Why it’s risky: These often contain nitrates and preservatives that can form harmful compounds like cholesterol oxidation products (COPs) when microwaved. COPs are linked to heart disease.
Safer alternative: If reheating is necessary (e.g., for pregnant individuals to avoid listeria), use a skillet or toaster oven to heat thoroughly without charring.
10. Chili Peppers
Why it’s risky: Capsaicin—the compound that makes peppers spicy—becomes volatile when heated. Microwaving can release capsaicin vapor into the air, which can irritate your eyes, throat, and lungs when you open the door.
Safer alternative: Add fresh peppers after reheating, or gently warm chili on the stovetop with the lid slightly ajar.
Final Tips for Safe Reheating
- Always store leftovers within 2 hours of cooking (1 hour if room temperature is above 90°F/32°C).
- Reheat only once—multiple reheating cycles increase bacterial risk.
- Use a food thermometer to ensure internal temperature reaches 165°F (74°C).
- Stir and rotate food halfway through microwaving if you must use it, to promote even heating.
