Doctors Warn: These 4 Foods Can Carry Parasites—What You Should Know Before Eating Them

Seafood can be an excellent source of protein, omega-3 fatty acids, vitamins, and minerals. But when certain seafood is eaten raw or undercooked, there is a potential risk of exposure to parasites and other foodborne pathogens.

Social-media posts often make dramatic claims that particular foods are “loaded with parasites” or should never be eaten. The reality is more nuanced. Not every piece of seafood contains parasites, and properly cooked seafood is generally much safer. The biggest concern is preparation, sourcing, storage, and cooking temperature.

Here are four categories of foods where parasite exposure can be a legitimate food-safety concern.

1. Raw or Undercooked Fish

Certain fish can carry parasites such as Anisakis, a type of roundworm that can infect people who consume raw or inadequately cooked marine fish.

Anisakis infection, sometimes called anisakiasis, can cause symptoms such as:

• Sudden abdominal pain
• Nausea
• Vomiting
• Diarrhea
• Occasionally an allergic reaction

Symptoms can occur relatively soon after eating infected raw or undercooked fish.

This is one reason dishes such as sushi, sashimi, ceviche, and lightly cooked fish require careful handling.

However, this does not mean that sushi automatically contains parasites. Commercial seafood intended for raw consumption may undergo parasite-control procedures such as appropriate freezing, depending on local regulations and the species and supply chain.

Cooking fish thoroughly is one of the most reliable ways to eliminate many parasites.

2. Squid and Other Cephalopods

The image accompanying the viral claim highlights squid, and there is a legitimate food-safety reason to pay attention to squid when it is eaten raw or insufficiently cooked.

Squid can harbor parasites, and raw seafood can also carry bacteria and viruses unrelated to parasites.

Eating squid thoroughly cooked significantly reduces these risks.

If you're preparing fresh squid at home, proper refrigeration and hygienic handling are also important. Don't leave raw seafood sitting at room temperature for extended periods.

And if squid has an unusual odor, appearance, or storage history, don't take chances simply because it looks fresh.

3. Crabs and Other Shellfish

Crabs can also be associated with parasitic infections when they are consumed raw or undercooked.

One notable example is Paragonimus, a parasitic lung fluke associated particularly with eating raw or undercooked freshwater crustaceans in areas where the parasite occurs.

Infection can eventually affect the lungs and may cause symptoms including:

Persistent cough, chest discomfort, fever, fatigue, or coughing up blood.

The important point is that the risk depends heavily on the species, geographic region, and preparation method.

A properly cooked crab is very different from raw or inadequately cooked crab.

Crab should therefore be cooked thoroughly rather than relying on appearance alone to determine whether it is safe.

4. Freshwater Fish

Freshwater fish deserve particular attention because some species can transmit parasitic infections when eaten raw or undercooked.

Examples include certain fish-borne flukes and tapeworms. Depending on the parasite, infection can affect the digestive tract, liver, or other organs.

Some infections cause few symptoms initially, while others can lead to:

• Abdominal discomfort
• Diarrhea
• Fatigue
• Poor appetite
• Weight loss
• Nutritional problems

Some fish-borne parasites can also cause more serious complications if infection persists for a long time.

This is why traditional dishes involving raw or fermented freshwater fish require particularly careful consideration of food-safety practices and local parasite risks.

The Biggest Myth: “You Can See the Parasites”

One problem with viral food-safety posts is that photographs of worms are frequently presented as proof that an entire category of food is dangerous.

But you cannot reliably determine whether seafood is safe simply by looking at it.

Some parasites may be visible, while others are microscopic or difficult to identify. Likewise, food can contain harmful bacteria or viruses without showing any obvious change in color, smell, or texture.

So don't rely on visual inspection alone.

Proper handling and cooking matter far more.

How Cooking Helps Protect You

For seafood, thorough cooking is one of the most important defenses against parasites.

The U.S. Food and Drug Administration generally recommends cooking seafood to an internal temperature of 145°F (63°C). A food thermometer is much more reliable than judging doneness by color alone.

If you're preparing seafood at home:

Keep it refrigerated.

Don't allow raw seafood to sit unrefrigerated for prolonged periods.

Prevent cross-contamination.

Use separate utensils and cutting surfaces for raw seafood when possible, and wash hands and kitchen surfaces thoroughly after handling it.

Cook seafood thoroughly.

Especially avoid eating raw or partially cooked seafood when you don't know whether appropriate parasite-control measures have been used.

Be especially cautious with high-risk populations.

Pregnant people, young children, older adults, and people with weakened immune systems can face greater consequences from certain foodborne infections.

What About Freezing Seafood?

Freezing can be an important parasite-control method for some seafood intended to be eaten raw.

However, freezing is not a universal substitute for cooking, and the effectiveness depends on the temperature, duration, parasite, species, and applicable food-safety standards.

Also, freezing does not necessarily eliminate every foodborne pathogen.

If you're buying seafood specifically for raw consumption, purchase it from a reputable supplier and follow the supplier's and local health authority's guidance.

Don't Panic If You Eat Seafood

Seeing a viral headline saying that a food is “full of parasites” can make it sound as though eating that food is almost guaranteed to cause an infection.

That's not how foodborne parasite risk works.

Millions of people eat seafood safely. The concern is primarily associated with specific foods, specific parasites, and inadequate preparation.

You don't need to eliminate seafood from your diet simply because parasites are possible.

Instead, focus on the basics:

Buy seafood from reputable sources.

Keep it properly refrigerated.

Prevent cross-contamination.

Cook it thoroughly unless it has been specifically prepared for safe raw consumption under appropriate controls.

Be particularly careful with raw or undercooked freshwater fish and crustaceans.

When Should You See a Doctor?

If you've eaten raw or undercooked seafood and subsequently develop severe abdominal pain, persistent vomiting, prolonged diarrhea, fever, difficulty breathing, or an unusual allergic reaction, seek medical advice.

More importantly, don't assume that every stomach problem after eating seafood is caused by parasites. Food poisoning, viral gastroenteritis, bacterial infections, food allergies, and other conditions can produce similar symptoms.

A healthcare professional can determine whether testing or treatment is necessary.

The Bottom Line

The claim that these foods are simply “loaded with parasites” is overstated. Seafood can contain parasites, but the risk varies considerably according to the species, origin, handling, and preparation.

Raw and undercooked seafood carries more risk than properly cooked seafood.

So rather than fearing every crab, squid, or fish you see at the market, use a smarter approach: choose reputable seafood, handle it safely, and cook it thoroughly.

That way, you can continue enjoying the nutritional benefits of seafood while dramatically reducing the risk of parasite-related foodborne illness.