What are the risks of eating eggshells?

January 13, 2026 •

5 min read

Studies show that while eggshells are a rich source of calcium, they may carry bacteria like Salmonella enteritidis, posing a food poisoning risk if not properly prepared. Therefore, understanding the significant risks of eating eggshells, even for their nutritional value, is critical.

Quick Summary

Ingesting unprepared eggshells can lead to bacterial infections from pathogens like Salmonella, and sharp fragments can cause internal injury. Proper sterilization and grinding are necessary to mitigate these dangers and safely utilize eggshells as a calcium source.

Key Points

Bacterial Contamination: Eggshells can harbor dangerous bacteria like Salmonella, which can cause severe food poisoning if not properly sterilized by boiling.
Physical Injury: Ingesting raw or coarsely ground eggshells can cause cuts and damage to the throat, esophagus, and other parts of the digestive system due to sharp fragments.
Heavy Metal Presence: Trace amounts of heavy metals like lead and aluminum can be found in eggshells, posing a risk with long-term, high-dose consumption.
Risk of Overdose: A single eggshell contains more than the recommended daily calcium intake, and excessive intake can lead to hypercalcemia and kidney stones.
Proper Preparation is Crucial: Sterilizing eggshells through boiling and baking, followed by grinding into a very fine, flour-like powder, is essential to mitigate risks.
Safer Alternatives Exist: Given the risks and intensive preparation required, safer sources of dietary calcium, such as dairy and leafy greens, are widely available.
Consult a Professional: Always speak with a healthcare provider before using homemade eggshell powder as a supplement, especially if you have existing health conditions.

Introduction to Eggshells as a Calcium Source

Eggshells are a natural and highly concentrated source of calcium, which is essential for bone health. One gram of eggshell can provide up to 400 mg of calcium, with some research suggesting it is absorbed effectively by the body. This has led some to explore using eggshell powder as an inexpensive supplement. However, the path from waste product to dietary supplement is fraught with significant risks that must be carefully considered and managed. These risks primarily involve bacterial contamination, physical injury from sharp pieces, and potential exposure to heavy metals.

The Primary Risks of Consuming Eggshells

Bacterial Contamination: The Threat of Salmonella

One of the most serious and prevalent risks associated with eating eggshells is bacterial contamination. Eggshells can harbor harmful bacteria, particularly Salmonella enteritidis, which can cause severe food poisoning. This contamination can occur either through the hen's reproductive tract before the egg is even laid (vertical transmission) or from fecal matter and environmental exposure after laying (horizontal transmission). Simply washing the shells with water is not enough to eliminate these bacteria, and eating raw or under-sterilized eggshells presents a high risk of infection. Symptoms of a Salmonella infection include fever, abdominal cramps, diarrhea, and in severe cases, more serious complications.

Physical Injury from Sharp Fragments

Unlike commercial calcium supplements, which are finely processed, homemade eggshell powder can contain sharp, jagged pieces. If the shells are not ground into a very fine, uniform powder, these fragments can pose a significant danger during ingestion.

Throat and Esophagus Damage: Larger, sharp fragments can scrape, irritate, or even puncture the delicate lining of the throat and esophagus as they are swallowed.
Digestive Tract Irritation: Further along the digestive tract, these sharp pieces can cause internal damage, leading to pain and discomfort.
Choking Hazard: In extreme cases, a large piece of eggshell could become lodged in the throat, creating a serious choking hazard.

Potential Heavy Metal Exposure

Eggshells, like other natural calcium sources such as oyster shells, can contain trace amounts of toxic heavy metals, including lead, aluminum, and mercury. While the levels in eggshells are generally considered lower than in some other natural sources, long-term or excessive consumption could potentially lead to a buildup of these metals in the body. It is a concern that should be acknowledged, especially for those considering regular, high-dose supplementation from homemade sources. Commercial supplements are typically subject to stricter regulations to ensure they are free from harmful levels of contaminants.

Risk of Excessive Calcium Intake

Eggshells are incredibly calcium-dense, with half a shell providing approximately 1,000 mg—the recommended daily intake for most adults. However, taking too much calcium can also be harmful. This condition, known as hypercalcemia, can lead to serious health problems over time, especially when taking unregulated homemade supplements. The risks include:

Nausea and fatigue.
Kidney stone formation.
Calcium deposits in soft tissues.
Potential cardiovascular issues, though studies on this topic are ongoing.

Comparison of Eggshell Preparation Methods


Feature	Eating Raw/Unprepared Eggshells	Homemade Eggshell Powder	Commercial Calcium Supplements
Safety (Bacteria)	High risk of contamination (e.g., Salmonella).	Low risk if properly sterilized by boiling and baking.	Minimal risk, regulated for safety.
Safety (Physical)	High risk of internal injury from sharp fragments.	Low risk if pulverized to a fine powder.	Minimal risk, processed to a uniform, fine texture.
Heavy Metals	Potential trace amounts, unregulated.	Potential trace amounts, unregulated.	Monitored and regulated to meet safety standards.
Calcium Bioavailability	Effective source, but with major health risks.	Studies suggest it's well-absorbed.	Well-absorbed, standardized dosage.
Convenience	Not recommended due to major risks.	Requires time and effort for safe preparation.	Convenient, readily available, easy to dose.
Cost	Very low cost.	Low cost.	Higher cost than homemade powder, but safer.

The Correct and Safe Preparation Process

For those who choose to use eggshells as a homemade calcium supplement, proper preparation is non-negotiable to mitigate the risks. The process must include sterilization and grinding to ensure safety.

Clean the Shells: Rinse the eggshells thoroughly under running water to remove any visible dirt or egg white residue.
Boil to Sterilize: Place the rinsed eggshells in a pot of boiling water for at least 15 minutes. This is a critical step to kill any potential bacteria like Salmonella.
Dry Completely: After boiling, remove the shells and spread them on a baking sheet. Dry them in an oven at 250°F (120°C) for 15-20 minutes, or until completely dry. This removes all moisture, which is essential for proper grinding and storage.
Grind into a Fine Powder: Use a coffee grinder, high-powered blender, or mortar and pestle to pulverize the dried shells into an extremely fine powder, similar in texture to flour.
Sift and Store: Sift the powder through a fine-mesh sieve to remove any remaining large, sharp pieces. Store the finished powder in an airtight container in a cool, dry place.

Conclusion

While the nutritional appeal of utilizing eggshells for their high calcium content is understandable, the risks of bacterial contamination, physical injury from sharp fragments, and potential heavy metal exposure are significant and should not be overlooked. Consuming raw or improperly prepared eggshells is dangerous and not recommended under any circumstances. Even with careful homemade preparation, risks related to heavy metals and excessive calcium intake remain. For reliable and safe calcium supplementation, regulated commercial products are a more consistent and safer alternative. If you do choose to prepare eggshell powder at home, it is imperative to follow the correct sterilization and grinding procedures precisely to minimize the associated dangers. Consulting a healthcare professional before adding any new supplement to your diet is always the safest course of action.

Alternative Sources of Calcium

For those concerned about the risks of eating eggshells, many other safer and more convenient sources of calcium are available. These include:

Dairy products (milk, yogurt, cheese)
Leafy green vegetables (kale, spinach, broccoli)
Fortified foods (certain cereals, orange juice)
Canned fish with bones (sardines, salmon)
Calcium-set tofu
Legumes and beans
Nuts and seeds (almonds, chia seeds)

A Final Word on Safety

Never assume that because something is natural, it is automatically safe. The potential for bacterial contamination alone makes consuming unprepared eggshells a serious health hazard. By understanding the risks and taking appropriate precautions—or choosing safer alternatives—you can ensure your calcium intake benefits your health without putting you at risk. For further information on food safety standards, particularly concerning eggs and poultry, you can refer to the USDA's Food Safety and Inspection Service(https://www.fsis.usda.gov/food-safety/safe-food-handling-and-preparation/eggs/shell-eggs-farm-table).

Frequently Asked Questions

Accidentally swallowing a small, sharp piece of eggshell can cause minor irritation to your throat or digestive tract but is unlikely to cause serious harm. However, a significant risk of bacterial infection exists if the eggshell is not sterilized.

No. Cooking the egg's contents does not guarantee that the bacteria on the exterior of the shell have been killed. To sterilize the shell, it must be boiled separately for an extended period, typically at least 15 minutes.

Not necessarily. While homemade eggshell powder can provide effective calcium, it carries risks from potential heavy metal content and is not regulated like commercial supplements. Commercial supplements are also processed to eliminate physical and bacterial risks.

Symptoms of a Salmonella infection typically appear 12 to 72 hours after exposure and include fever, diarrhea, abdominal cramps, and sometimes nausea or vomiting. If you experience these symptoms after eating eggshells, seek medical attention.

Yes, some methods involve dissolving ground eggshells in an acid like lemon juice for several hours. This method relies on the acid to break down the calcium carbonate and may transfer the calcium into the liquid, though it may not fully address all contamination risks.

Excessive calcium intake can lead to hypercalcemia, which can cause symptoms like nausea, fatigue, kidney stone formation, and potentially contribute to cardiovascular issues over time. Since eggshells are so calcium-dense, moderation is key.

The same risks for humans apply to pets. If you intend to use eggshell powder as a calcium supplement for your pets, it is critical to follow the same sterilization and fine-grinding procedures as for human consumption. Always consult a veterinarian first.

Eggshells have several safe alternative uses. They can be crushed and added to garden soil or compost to enrich it with calcium, or used in a bird feeder to provide calcium for birds. They can also be used as a non-toxic abrasive for cleaning pots and pans.