What is the black stuff in eggs?

Table of Contents

Quick Answer

The black specks sometimes seen in eggs are called blood spots or meat spots. They are small blood vessels that ruptured when the egg was forming in the hen’s reproductive tract. Blood spots are harmless and do not indicate a fertilized egg. They can be removed by cracking the egg into a bowl and picking out the spots before cooking.

What Causes Blood Spots in Eggs?

Blood spots, also known as meat spots, are small dark red specks that can occasionally be seen on an egg yolk. They are caused by the rupture of a blood vessel on the yolk surface during egg formation. Here are some key facts about what causes blood spots in eggs:

As an egg develops, it goes through a cycle where blood vessels form on the yolk surface to nourish the growing embryo. In an unfertilized egg, these blood vessels naturally regress by the end of development.

If a blood vessel fails to regress properly, it may rupture and bleed into the egg prior to being laid. This causes the speckling of blood that appears as spots on the yolk.
Genetics play a role. Some breeds of hens tend to have higher occurrences of blood spots.
Stress, disease, genetics, age, and diet are factors that can influence the regression of blood vessels and lead to more blood spots.

The blood spots are more common in older hens, as their reproductive organs may be more prone to these ruptures occurring.

In the end, while unsightly, these spots are naturally occurring and harmless. They can be removed before cooking the egg.

Are Blood Spots an Indicator of a Fertilized Egg?

Many people wonder if blood spots mean the egg has been fertilized. The answer is no – blood spots do not indicate a fertilized egg. Here is why:

Fertilization occurs high up in the hen’s oviduct before the shell forms around the egg.
Blood spots occur later as the egg is nearly fully formed, just before being laid.
Blood vessels on the yolk surface are normal even in unfertilized eggs as part of embryonic development.

Blood spots simply mean a blood vessel ruptured. This can occur with or without fertilization.
Fertilized eggs are extremely rare in commercial egg production where hens and roosters are kept separated.

So while fertilized eggs with embryos do contain blood vessels, the presence of blood spots alone does not indicate fertilization has occurred. The spots can happen in any egg.

Are Blood Spots Safe to Eat?

Blood spots are perfectly safe to consume and do not make the egg unsafe or unhealthy. Here is some information on the safety of blood spots:

Blood spots are edible and made of the same components as blood.
Cooking the egg thoroughly will eliminate any food safety risks from bacteria.

Blood spots simply provide iron and small amounts of nutrients like vitamin B-12.
The spots do not indicate illness in the hen. It is a naturally occurring phenomenon.
Both the spot and the rest of the egg are fine to eat.

So while the appearance of blood spots may be unappetizing to some people, there are no health risks associated with consuming them. However, the spots can be removed before cooking if desired.

How to Remove Blood Spots from Eggs

While blood spots are harmless, some people prefer to remove them before cooking or eating an egg. Here are some tips for removing blood spots:

Crack the egg into a small bowl first, rather than directly into a hot pan or onto an egg dish.

Inspect the egg briefly for any visible spots after cracking.
Use the tip of a knife to gently lift and remove any spots from the yolk.
Discard the spots and then cook or consume the egg as normal.

Alternatively, use an egg separator tool to isolate the yolk before inspecting and removing spots.

Cracking the egg separately allows you to remove just the spot rather than having to discard the whole egg. With a little practice, spots can be easily removed this way before cooking.

Do Organic or Free-Range Eggs Have More Blood Spots?

There is some debate over whether organic, free-range, or cage-free eggs are more likely to contain blood spots than conventional eggs. Here is an overview:

Some studies have shown higher rates of blood spots in free-range eggs.
This may be because free-range hens are exposed to more parasites and predators, causing stress.
However, other studies have shown no difference in blood spot rates between differently raised eggs.

Blood spots increased with hen age across all housing types.
So there is no conclusive evidence that housing system impacts blood spot frequency.

In the end, all egg production systems and breeds of hen may experience some level of blood spots. No overwhelming evidence points to cage-free or pasture-raised eggs having higher rates than conventional eggs.

Are Blood Spots More Common in Certain Chicken Breeds?

Certain breeds and varieties of chickens do tend to have higher occurrences of blood spots in their eggs. Some key points:

Heritage breed chickens like Araucanas, Faverolles, and Legbars are prone to blood spots.
The Araucana is known for a higher likelihood of blood spots due to genetics.

Broiler-type birds bred for meat rather than egg laying also tend to have more blood spots.
In commercial flocks, there can be individual hens that are genetically prone to blood spots.
Rhode Island Reds, Leghorns, and other common laying breeds have a lower incidence.

So the breed of hen does play a role, with some breeds genetically predisposed to more issues with blood vessel regression and spotting. Heritage breeds tend to experience more spots.

Does Diet Impact Blood Spots in Eggs?

Some people wonder if a hen’s diet can affect the occurrence of blood spots in her eggs. Here is what we know about the link between diet and blood spots:

There is limited research showing that vitamin A deficiency may contribute to more blood spots.

Diets too high in fish products were linked to spots in one study.
However, most studies find no conclusive link between diet and blood spot rates.
Providing a balanced, nutritious diet is recommended to support hen health.

No specific dietary changes have been found to prevent blood spots.

Overall, the scientific evidence that diet impacts blood spots is weak. Ensuring good general nutrition supports hen health but may not directly impact blood vessel development in eggs. More research is needed on this topic.

Can Stress Increase Blood Spots?

It is well documented that stress can cause an increase in blood spot occurrence in chickens. Here are the key reasons why:

Stress hormones constrict blood vessels, which can lead to ruptures.
Chronic fear and stress impede the regression of blood vessels on the yolk.
Transport, handling, illness, and new environments can stress chickens.

One study found that inducing stress tripled the blood spot rate.
Minimizing stressors helps prevent issues like blood spots.

Managing stress through proper housing, gentle handling, and healthy environments is important for overall flock health and reducing defects like blood spots in eggs.

Do Blood Spots Affect Egg Quality or Taste?

Blood spots do not have any impact on the quality, flavor, nutritional value, or taste of an egg. Aside from the appearance, an egg with spots is the same as an egg without.

The yolk and white remain perfectly normal and safe to eat.
Cooking the egg makes blood spots indistinguishable in texture.

Any minor iron taste from the spots is unlikely to be noticeable.
The spots do not indicate age, freshness, or any defects besides the spots themselves.
Removing the spots results in an egg identical to one laid without them.

So while many people consider blood spots an egg quality defect for aesthetic reasons, they do not alter the eating experience. The egg can be consumed just fine with or without the spots.

Are Blood Spots More Common in Older Eggs?

Blood spots occur while the egg is forming in the hen, before the egg is laid. As a result, spots do not become more common or increase in number as the egg ages. Key facts:

An older egg may appear more spotty as the yolk thins and spreads.

But the number of actual blood spots does not change over time.
The spots are not related to egg freshness, just the hen’s reproductive system.
Storing eggs may make existing spots more visible but won’t create new ones.

Checking for blood spots can’t determine an egg’s age or freshness.

So while blood spots may be more visually obvious in older eggs, their incidence is unrelated to shell age. They are pre-existing, having occurred as the egg formed in the hen.

Are Double Yolks More Prone to Blood Spots?

Double yolks (two yolks in one egg) do seem more susceptible to having blood spots. There are a few reasons for this:

Double yolks put more strain on blood vessel regression in the hen’s reproductive tract.
The double mass of yolk tissue has an increased chance of vessels rupturing.
Double yolks are more common in young hens, which are also prone to blood spots.

One study found double yolks had 3 times as many spots versus single yolks.
So the irregularity of a double yolk contributes to spotting.

The double yolk essentially provides more surface area for spots to appear. While still harmless, the abnormal shape does make blood spots more likely to occur in these eggs.

Can Infection Cause Blood Spots?

Bacterial and viral infections are unlikely to cause or contribute to blood spots in eggs. Here is the reasoning:

Blood spots occur before an egg is laid due to vessel rupture.
Infections would have to be present in the hen’s reproductive tract.

Common egg-borne infections affect the albumen or yolk contents after laying.
Salmonella and other bacteria do not cause the blood vessel issues that lead to spots.
Illness stress could indirectly increase spots, but not through direct infection.

So while many diseases and pathogens can be egg-transmitted, the infection itself does not produce blood spots. Only reproductive illness in the hen could potentially impact the vessels.

Can Medications or Vaccines Cause Blood Spots?

There is no evidence that medications or vaccines routinely given to chickens cause or increase the occurrence of blood spots in eggs. Here are the key reasons:

No studies directly link medications to blood spot development.

Spots are caused by vessel rupture in egg formation, not external factors.
Some illness or stress could indirectly increase spots.
Improper injection technique could potentially damage vessels.

But proper administration of medications should not affect blood spots.

In general, routine medications and vaccines given to commercial flocks are not considered to have any effect on blood spot development or frequency. There is no reason to believe properly administered treatments would contribute to blood spots in eggs.

Does Altitude Affect Blood Spots?

A few studies have suggested that eggs laid at higher altitudes may potentially have a higher incidence of blood spots. Reasons for this possible correlation are not well understood but could include:

Lower air pressure at altitude may place more strain on blood vessels.
Transportation to higher elevations may stress the hen’s reproductive system.
Oxygen availability differences could play a role.

Not all studies have found a strong or consistent link.
So while anecdotally reported, altitude is not a proven factor.

Much more research is needed to analyze if lower atmospheric pressure or other high-altitude factors could increase fragility of blood vessels in developing eggs. Currently, there is insufficient evidence to draw conclusions.

Can You Prevent Blood Spots in Eggs?

There is no foolproof method to completely prevent blood spots, but some strategies may help reduce their likelihood:

Selecting bird breeds less prone to spotting.
Avoiding stressors and providing an optimal environment.

Following a balanced diet with adequate nutrients.
Allowing hens to follow natural lighting cycles.
Culling individual birds with chronic high rates of spots.

Checking for spots routinely and removing affected eggs.

While not guaranteed to eliminate spots entirely, focus on healthy hens and minimizing stress. Be sure to cook eggs thoroughly as an additional precaution if concerned.

Conclusion

Blood spots are a natural occurrence in eggs resulting from the rupture of small blood vessels on the yolk surface. While visually unappealing, they pose no health risks or impacts on egg quality. Blood spots are reasonably common and hens genetically prone to vessel issues produce more of them. Care should be taken to minimize stress, while cooking eggs thoroughly eliminates any possible food safety concerns. With some simple practices, blood spots can bemanaged appropriately.