Why Can't You Eat Crab? Understanding the Risks and Dietary Restrictions

November 3, 2025 •

5 min read

Shellfish, including crab, is the leading cause of self-reported food allergies in U.S. adults, affecting approximately 3%. While generally healthy, there are critical reasons why can't you eat crab in certain situations, ranging from allergic reactions to contamination from toxins and heavy metals.

Quick Summary

Explore the crucial reasons to avoid crab, such as severe allergies, heavy metal and toxin contamination in certain parts, and the risks associated with consuming it raw or undercooked.

Key Points

Shellfish Allergy: A primary reason to avoid crab, as it can trigger severe, life-threatening allergic reactions like anaphylaxis.
Heavy Metal Contamination: The hepatopancreas, or 'tomalley', can accumulate high levels of toxic heavy metals like cadmium, making it unsafe for frequent consumption.
Risk for Pregnant Women: Due to potential bacteria, parasites, and allergy risks, pregnant women must ensure crab is thoroughly cooked and limit consumption.
Raw Crab is Dangerous: Raw or undercooked crab can contain harmful bacteria (e.g., Vibrio) and parasites (e.g., lung flukes), leading to foodborne illnesses.
Avoid Inedible Parts: The gills ('dead man's fingers') and internal organs ('tomalley') should be discarded to avoid ingesting toxins, contaminants, and unpleasant textures.
High Sodium Content: People with hypertension, kidney disease, or gout should be mindful of crab's high sodium content and consume it in moderation.

Who Needs to Avoid Crab?

Despite being a delicious and nutrient-rich food, crab is not safe for everyone. There are several population groups who should exercise caution or avoid it entirely due to various health concerns. The primary concerns revolve around allergies, contaminants, and specific health conditions that make consumption risky.

People with Shellfish Allergies

Shellfish allergy is a common condition that can cause a range of symptoms, from mild to life-threatening. The immune system overreacts to proteins found in shellfish, such as tropomyosin. For those with a shellfish allergy, consuming crab can trigger a severe reaction known as anaphylaxis. Since cross-reactivity is common among crustaceans, someone allergic to shrimp, for example, is likely also allergic to crab. Even exposure to cooking vapors can cause a reaction in highly sensitive individuals. The only proven therapy for a crustacean allergy is complete avoidance.

Pregnant Women

While many types of seafood are encouraged during pregnancy for their omega-3 fatty acids, pregnant women must be cautious with crab consumption. The main risks include potential exposure to bacteria and parasites if the crab is not cooked thoroughly. Some studies also suggest that pregnant women with a known allergic constitution should be careful, as a reaction could also impact the baby. It is crucial to ensure crab is fully cooked to an internal temperature of 145°F to eliminate harmful pathogens.

Individuals with Compromised Immune Systems

Similar to pregnant women, people with compromised immune systems are more susceptible to foodborne illnesses from bacteria and viruses found in raw or improperly prepared seafood. Given that crabs can harbor bacteria like Vibrio, this group should only eat crab that has been cooked thoroughly and handled safely.

People with Certain Health Conditions

Certain pre-existing health conditions can be exacerbated by eating crab. The reasons are varied:

High Blood Pressure and Kidney Issues: Crab contains a high amount of sodium. For individuals with hypertension or kidney disease, excessive sodium intake can be problematic.
Gout: This condition is caused by a buildup of uric acid. While not as high in purines as some other seafood, crab is not an ideal choice for those with a history of gout.
Biliary Diseases: People with conditions like cholecystitis or gallstones, often related to excess cholesterol, should avoid or limit crab. The tomalley, or crab mustard, is high in cholesterol and can worsen these conditions.

Health Risks Associated with Crab Consumption

Even for those without specific dietary restrictions, several risks are associated with consuming crab, primarily related to environmental factors and preparation methods.

Contaminants and Heavy Metals

Crabs, as bottom-feeders, can accumulate contaminants from their environment. These include heavy metals and natural toxins.

Cadmium: The brown meat or tomalley of crabs is known to accumulate higher levels of cadmium than the white meat. Cadmium is a toxic heavy metal that can cause health problems if consumed in large quantities over time.
Mercury: While generally lower in mercury than large predator fish, crab can still contain varying levels, depending on the source. However, the levels are not as concerning as for fish like shark or swordfish.
Biotoxins: Crabs can absorb natural biotoxins from toxic algal blooms. These can lead to serious illnesses like paralytic shellfish poisoning (PSP). Cooking does not always destroy these toxins.

Parasites and Foodborne Illness

Raw or undercooked crab poses a risk for parasitic infections and bacterial illnesses.

Bacteria: Raw crab can harbor bacteria such as Vibrio parahaemolyticus, which can cause gastrointestinal issues.
Parasites: Consuming raw or undercooked crab meat can lead to parasitic infections. One notable example is the lung fluke, Paragonimus westermani, which can cause a condition called paragonimiasis.

High Sodium

Crab meat, especially in processed or canned form, can be quite high in sodium. This is a concern for people monitoring their sodium intake for heart health or blood pressure control.

Safe vs. Unsafe Crab Consumption

Making informed choices about crab consumption depends on understanding the risks and practicing safe preparation. The following table compares safe practices with those that pose health risks.


Aspect	Safe Practices	Unsafe Practices
Sourcing	Reputable vendors, known clean waters.	Unknown or unmonitored sources.
Preparation	Cooked thoroughly (145°F), meat is opaque and flaky.	Raw, undercooked, or refrigerated smoked crab.
Handling	Separate raw and cooked seafood, wash hands/surfaces.	Cross-contamination with other foods.
Parts to Eat	White meat from legs and claws.	Gills ('dead man's fingers'), tomalley ('mustard'), internal organs.
Consumption	Moderation, especially for at-risk groups.	Excessive amounts, especially of high-cadmium parts.

Key Considerations for Safe Crab Eating

To enjoy crab while minimizing risks, consider these points:

Choose Freshness: Opt for fresh, lively crabs with intact shells from reputable suppliers.
Cook Thoroughly: Heat is your best defense against bacteria and parasites. Ensure the meat is opaque and flaky throughout.
Avoid Raw: Never consume raw or undercooked crab. This includes dishes like ceviche that use raw or lightly marinated shellfish.
Stick to the White Meat: Focus on the sweet white meat from the legs and claws, as the internal organs and gills carry higher risks of contaminants and toxins.
Practice Good Hygiene: Prevent cross-contamination by keeping raw and cooked crab separate and washing all surfaces and utensils.

The Inedible Parts of a Crab

Beyond the meat, a few parts of a crab should be discarded for safety and taste reasons. These include:

The Gills: Known as 'dead man's fingers', these feathery, cone-shaped gills are not toxic but are tough, chewy, and bitter. They do not contain meat and should be removed before eating.
The Tomalley: This soft, greenish-yellow substance, also called 'crab mustard', is the hepatopancreas—a digestive gland. While considered a delicacy by some, it can contain high levels of toxins and heavy metals like cadmium. For most, especially those with health concerns, it is best to avoid it.
The Roe: Crab roe or eggs, while edible, can contain toxins if the crab has been feeding on toxic algae. If the source is not known to be safe, it is best to discard it.

Conclusion: Making an Informed Choice

While crab can be a healthy and delicious part of a diet, the question of "why can't you eat crab?" reveals important exceptions and risks that should not be ignored. Severe shellfish allergies pose the most immediate danger, while contaminants like heavy metals and biotoxins, primarily found in the internal organs, present a more subtle, long-term risk. Additionally, consuming raw or undercooked crab can lead to foodborne illnesses and parasitic infections. By understanding who is at risk, avoiding the inedible parts, and always cooking crab thoroughly, consumers can enjoy this seafood safely. For those with allergies or specific health conditions, complete avoidance is the only sure path to safety.

Frequently Asked Questions

Yes, pregnant women can eat crab, but it must be fully cooked to an internal temperature of 145°F to eliminate harmful bacteria and parasites. It is also recommended to limit consumption to 8-12 ounces per week and avoid the tomalley due to potential contaminants.

You should not eat the gills, commonly called 'dead man's fingers,' as they are tough and bitter. The internal organs, especially the greenish-yellow tomalley, can contain high levels of heavy metals and toxins and should be avoided.

The 'mustard', or tomalley, is a digestive gland that can accumulate high levels of heavy metals like cadmium. While some consider it a delicacy, health advisories often recommend avoiding it, especially for vulnerable groups like pregnant women.

The primary danger of eating raw crab is exposure to foodborne illnesses from bacteria like Vibrio and parasites such as lung flukes, which are eliminated through proper cooking.

Individuals with shellfish allergies are most at risk, as exposure to crab, even through cooking vapors, can cause severe reactions like anaphylaxis. Cross-reactivity means an allergy to one crustacean often means an allergy to all.

Yes, excessive crab consumption can be harmful due to its high sodium content, which can impact those with hypertension or kidney issues. Overconsumption of the tomalley can also lead to an unsafe buildup of heavy metals.

Yes, some species of crabs are inherently toxic. Additionally, crabs can absorb natural biotoxins from harmful algal blooms in certain waters, which may not be destroyed by cooking. Using local fish advisories is recommended.

Crab generally has low levels of mercury compared to many other types of seafood, especially large predator fish like swordfish or bigeye tuna. However, contaminants can vary by source, so it's best to consume in moderation as part of a varied diet.