Why are crustaceans bad for you? Unpacking the health risks

January 11, 2026 •

3 min read

According to the Centers for Disease Control and Prevention, an estimated 80,000 cases of vibriosis occur in the United States each year, often linked to contaminated shellfish. While often celebrated for their nutritional value, there are several key reasons why crustaceans can be bad for you, particularly if not handled, prepared, or consumed correctly.

Quick Summary

The potential dangers of eating crustaceans include severe allergic reactions, foodborne illness from bacteria and viruses, accumulation of environmental toxins like heavy metals, and high purine content that can trigger gout. Careful handling and proper cooking are essential to minimize risks.

Key Points

Allergy Risk: Crustacean allergies, caused by the protein tropomyosin, are a common and potentially life-threatening food allergy that typically develops in adulthood.
Foodborne Illness: Consuming raw or undercooked crustaceans can lead to dangerous infections from bacteria like Vibrio, viruses such as Norovirus, and parasites.
Heavy Metal Contamination: Some crustaceans can accumulate harmful heavy metals like cadmium, mercury, and lead from polluted environments, posing a long-term health risk with heavy consumption.
Gout Trigger: The high purine content in many crustaceans can increase uric acid levels, potentially triggering painful gout attacks in susceptible individuals.
Cholesterol Misconception: While high in dietary cholesterol, the low saturated fat content of crustaceans means they do not significantly impact blood cholesterol levels for most healthy people.
Preparation Matters: Health benefits can be compromised by unhealthy cooking methods like frying; steaming, boiling, or baking are healthier alternatives.

Allergic Reactions: The Most Common and Severe Risk

Among the various health concerns, shellfish allergy is one of the most prevalent and can be life-threatening. Shellfish allergies typically develop in adulthood and are a leading cause of food-induced anaphylaxis. The primary allergen is a muscle protein called tropomyosin, which is highly conserved across different crustacean species, leading to cross-reactivity. This means if you are allergic to one crustacean, like shrimp, you are likely allergic to others, such as crab and lobster.

Symptoms of a shellfish allergy

Mild symptoms: Hives, itching, swelling of the lips, tongue, or throat.
Severe symptoms: Wheezing, difficulty breathing, dizziness, and life-threatening anaphylactic shock.

Foodborne Illness from Contamination

Crustaceans, like other shellfish, can filter bacteria, viruses, and parasites from their watery environments. Consuming raw or undercooked shellfish significantly increases the risk of foodborne illnesses. This is particularly true during warmer months when bacteria like Vibrio flourish. Cooking thoroughly is the most effective way to destroy these harmful organisms. However, some marine toxins are not destroyed by cooking.

Common pathogens in crustaceans

Vibrio bacteria: Found naturally in coastal waters, it can cause severe gastrointestinal issues and skin infections.
Norovirus and Hepatitis A: Can contaminate shellfish in waters affected by sewage.

Accumulation of Toxins and Heavy Metals

Another reason crustaceans can be bad for you relates to what they absorb from their environment. Crustaceans are filter feeders or scavengers, and some species can accumulate harmful heavy metals such as cadmium, mercury, and lead. While many commercial crustaceans, like shrimp and scallops, are considered low in mercury, levels can vary by species and location.

Heavy metals and health

Accumulated heavy metals are difficult for the human body to excrete and can cause long-term organ damage, especially to the brain and kidneys.
Brown crab meat, in particular, has been found to have higher concentrations of heavy metals, including cadmium, compared to the white meat.

Gout and High Purine Content

For individuals with a history of gout, a form of inflammatory arthritis, consuming crustaceans can trigger painful flare-ups. This is because many shellfish are high in purines, which are compounds that the body breaks down into uric acid. Excess uric acid can form sharp, needle-like crystals in the joints, causing severe pain and swelling. While some crustaceans like canned clams may have lower levels, high-purine varieties include shrimp, lobster, and crab.

Comparison of Potential Crustacean Risks


Health Concern	Primary Cause	Risk Severity	How to Mitigate Risk
Allergies	Tropomyosin protein	High (can be life-threatening)	Strict avoidance of all crustaceans; carry an epinephrine auto-injector.
Food Poisoning	Bacteria, viruses, parasites	Moderate to high	Buy from reputable sources; ensure proper storage and thorough cooking.
Heavy Metals	Environmental bioaccumulation	Low to moderate (depends on consumption)	Moderate overall intake; choose lower-mercury varieties like shrimp.
Gout	High purine content	Variable (depends on individual)	Limit consumption, especially during flare-ups; consult a doctor or dietitian.

Addressing the High Cholesterol Myth

Historically, crustaceans were often seen as unhealthy due to their high cholesterol content. However, modern nutritional science shows this concern is largely misplaced for most people. Shrimp and lobster are high in cholesterol, but they are low in saturated and trans fats, which have a much greater impact on blood cholesterol levels. Furthermore, shrimp can increase levels of both 'good' (HDL) and 'bad' (LDL) cholesterol, maintaining a healthy balance. The key is moderation and preparation method; frying them adds saturated fat that negates their benefits. For most healthy individuals, the cholesterol in crustaceans is not a significant health concern.

Conclusion

While many people can safely enjoy crustaceans as part of a balanced diet, the question of "why are crustaceans bad for you" is a valid one with several important considerations. The most significant risks are severe allergic reactions and foodborne illnesses from improper handling or preparation. The accumulation of heavy metals is a long-term concern for heavy consumers, and the high purine content makes them a poor choice for those with gout. With careful purchasing, thorough cooking, and an understanding of individual health needs and allergies, the risks can be managed. Always consult a healthcare professional for personalized dietary advice, especially if you have an underlying health condition. Click here for more information on managing shellfish allergies.

Note: It is critical for individuals with known shellfish allergies to completely avoid crustaceans and any products that may have come into contact with them.

Frequently Asked Questions

No, while thorough cooking kills bacteria and viruses that cause food poisoning, it does not destroy marine toxins like those from algal blooms or remove accumulated heavy metals.

No, a shellfish allergy is distinct from a fish allergy, although it is possible to have both. The allergens in crustaceans are different from those in finfish.

If you have gout, you should generally limit or avoid most crustaceans, as they are high in purines. Seafood high in purines that should be limited includes shrimp, crab, and lobster.

Symptoms can vary depending on the pathogen but often include diarrhea, stomach cramps, nausea, vomiting, and fever.

Not necessarily. The safety depends on the source. Both farmed and wild-caught crustaceans can carry risks of contamination, pollutants, and disease if not harvested or processed correctly.

It is often impossible to tell if shellfish is contaminated by look, smell, or taste. This is why purchasing from reputable suppliers and ensuring proper handling and cooking are critical safety measures.

For most healthy people, no. While high in cholesterol, shrimp is low in saturated fat, which has a greater impact on blood cholesterol. The health benefits, including omega-3 fatty acids, often outweigh the dietary cholesterol concerns.