Do Eggs Have Parasites in Them? Separating Fact from Fiction

November 26, 2025 •

4 min read

While highly uncommon, reports exist of parasitic worms being found inside chicken eggs. Although the primary food safety risk associated with eggs is bacterial contamination, especially Salmonella, the possibility of parasites does exist under specific, unusual conditions. This article clarifies whether do eggs have parasites in them and outlines the crucial differences between parasitic and bacterial contamination.

Quick Summary

This guide explains the difference between parasites and bacteria in eggs. It covers the extreme rarity of finding parasites, the conditions under which it might occur, and emphasizes that bacterial risks are the most common concern. It also provides essential food safety tips for preventing contamination and ensuring safe egg consumption.

Key Points

Parasites are Extremely Rare: Finding parasites like worms inside a hen's egg is a very rare biological anomaly, not a routine food safety concern.
Bacteria are the Real Threat: The primary risk from egg contamination comes from bacteria, such as Salmonella, which is microscopic and cannot be seen or smelled.
Proper Cooking is Key: Thoroughly cooking eggs until the yolk and white are firm is the most effective way to kill any bacteria that might be present.
Vulnerable Populations Need Extra Caution: Raw or undercooked eggs should be avoided by young children, the elderly, pregnant women, and the immunocompromised.
Practice Good Hygiene: Always wash your hands and sanitize kitchen surfaces after handling raw eggs to prevent cross-contamination.
Refrigeration is Essential: Store eggs in the main part of the refrigerator to slow bacterial growth and ensure safety.
Pasteurized Eggs for Raw Use: For recipes that call for raw eggs, using pasteurized egg products significantly reduces the risk of Salmonella infection.

Understanding the Risk of Parasites in Eggs

The thought of parasites in our food is unsettling, and for eggs, it's a common fear rooted in misconceptions. It's crucial to understand that while bacterial contamination, such as Salmonella, is a well-documented risk, the presence of macroscopic parasites—like worms—inside a hen's egg is an exceptionally rare biological anomaly, not a routine threat to human health. Most people will never encounter a parasitic inclusion in an egg from a reputable commercial source.

Why Do Parasites Sometimes Appear in Eggs?

The rare instances of parasites being found in eggs are linked to the hen's health and anatomy. The chicken's digestive, reproductive, and urinary systems converge at a single exit point called the cloaca. While the egg normally passes through the oviduct in a one-way process, certain extreme conditions can lead to cross-contamination.

Conditions that can increase the risk of parasitic migration include:

High parasite burden: A hen with a severe parasitic worm infection has a greater chance of worms migrating to other parts of its body, including the oviduct where the egg forms.
Compromised immune system: A weakened immune response in the hen can make it more susceptible to heavy infestations and aberrant parasite migration.
Poor husbandry: Overcrowded coops, unsanitary living conditions, and stress can exacerbate parasitic infections in a flock.
Cloacal reflux: A rare reversal of flow where material from the cloaca re-enters the oviduct can introduce parasites or their eggs.

Differentiating Parasites from Bacteria

For consumers, it is far more important to understand bacterial risks than parasitic ones. Bacteria like Salmonella can be present inside or on the surface of an egg and are the leading cause of egg-related foodborne illness. These microscopic organisms cannot be seen or smelled. In contrast, a parasitic worm is a macroscopic organism, and its presence would likely be visible upon cracking the egg.


Aspect	Parasites (e.g., Ascaridia galli)	Bacteria (e.g., Salmonella)
Appearance	Visible as a small worm, often in the egg white.	Microscopic, invisible to the naked eye.
Location	Extremely rare inside the egg; results from worm migration or contamination in the oviduct.	Can be inside the egg (trans-ovarian) or on the shell.
Occurrence	Very rare; considered a biological anomaly linked to severe infections in the hen.	Common cause of foodborne illness worldwide; a significant public health concern.
Cause	Aberrant migration of worms from the intestinal tract to the oviduct.	Infection transferred from the hen to the egg during its formation or from droppings on the shell.
Risk to Humans	Highly unlikely risk, but ingestion of a parasitic worm is a possibility if an infected egg is consumed.	High risk of food poisoning if consumed raw or undercooked, especially for vulnerable populations.

The Importance of Proper Egg Handling and Cooking

Given that the far more significant risk comes from bacteria, practicing proper egg handling and cooking techniques is essential for food safety. The U.S. Department of Agriculture (USDA) and similar health authorities worldwide emphasize that cooking eggs thoroughly is the most effective way to eliminate harmful bacteria like Salmonella.

Best practices for egg safety:

Purchase refrigerated eggs: Always buy eggs from a refrigerated case and check the expiration or “use by” date.
Refrigerate promptly: Store eggs in their original carton in the main part of your refrigerator, not the door, where temperatures can fluctuate.
Inspect and discard: Never use eggs that are cracked or have dirty shells. Bacteria from the shell can easily enter the porous egg.
Avoid washing eggs: Commercial eggs are typically washed and sanitized before packaging. Washing them at home can remove the protective coating and increase the risk of bacterial entry.
Cook thoroughly: Cook eggs until both the white and yolk are firm. This practice kills any bacteria that may be present, making them safe for consumption. For dishes containing eggs, such as casseroles, ensure they reach an internal temperature of 165°F (74°C).
Handle with clean hands: Wash your hands, utensils, and surfaces with hot, soapy water before and after handling raw eggs to prevent cross-contamination.

What About Raw or Undercooked Eggs?

Eating raw or undercooked eggs poses a higher risk of Salmonella infection. Certain recipes, such as Caesar salad dressing, mayonnaise, or hollandaise sauce, traditionally call for raw eggs. For these preparations, using pasteurized eggs is highly recommended, especially when serving vulnerable groups like pregnant women, young children, or the elderly. Pasteurization involves heating the eggs just enough to kill bacteria without cooking them.

Conclusion

While the concept of parasites in eggs can be alarming, it is a near-zero risk for most consumers, particularly for commercially produced eggs. The primary concern and focus for safe egg consumption should be on preventing bacterial contamination, most notably from Salmonella. By following proper handling, storage, and cooking guidelines, you can safely enjoy eggs and minimize any risk of foodborne illness. Understanding the minute differences between parasitic and bacterial threats helps provide peace of mind and allows for informed and safe food preparation.

Visit FoodSafety.gov for more information on safe egg handling and preparation guidelines.

Frequently Asked Questions

Yes, it is possible but extremely rare. Parasitic worms, such as the roundworm Ascaridia galli, have occasionally been reported inside chicken eggs. This occurs under specific, unusual conditions within the hen, often involving severe infections where the worms aberrantly migrate from the intestinal tract to the oviduct.

The biggest risk by far is bacterial contamination, primarily Salmonella. Unlike microscopic bacteria which are a common food safety concern, parasitic infestations are exceptionally rare in commercially produced eggs and are considered a biological anomaly.

If an egg contained a macroscopic parasite like a worm, it would likely be visible upon cracking the egg open, often appearing as a small, thin inclusion in the egg white. Bacterial contamination, however, is not visible to the naked eye.

Yes, thorough cooking is effective at killing both parasites and harmful bacteria like Salmonella. Cooking eggs until the yolk and white are firm is the best way to ensure they are safe to eat.

The risk is not tied to whether an egg is 'farm-fresh' versus commercial. The likelihood of parasites is linked to the individual hen's health and hygiene of its environment. Poor husbandry and heavy parasite burdens can increase risk in any setting.

Salmonella can contaminate eggs in two ways: either while the egg is still forming inside the hen (trans-ovarian contamination) or by penetrating through the porous shell after it has been laid and come into contact with bacteria from the hen's droppings.

Eating raw or undercooked eggs is not recommended due to the risk of Salmonella infection. Vulnerable individuals, including young children, the elderly, and pregnant women, should always avoid raw eggs and any foods containing them, such as homemade mayonnaise or hollandaise sauce made with unpasteurized eggs.