There are few things as unsettling as groggily cracking open an egg for your breakfast only to find a mysterious spot in or around the yolk.
Fear not, though — more often than not, these spots are harmless. If your eggs come from your own backyard flock, they may even lend insights about your chickens’ living conditions.
Small, reddish-brown spots are blood spots, which are caused from a rupture on the yolk surface during egg formation inside the hen. These spots can range in appearance, from nearly indistinguishable spots on the surface of the yolk to spots diffused through the white of the egg, also known as the albumen.
“Essentially, they are part of the internal story of what goes on with an egg,” said Anne Lichtenwalner, director of the University of Maine Veterinary Diagnostic Laboratory. “Eggs are complicated reproductive events that occur inside the bird. Everything is being applied in layers by this organ that we refer to as the reproductive tract or the oviduct. The thing about the red spots is that’s where there’s been a small hemorrhage in the oviductal tissue in the part that the hen is creating and excreting that material.”
These blood spots are generally harmless, but there are a number of things that could cause these blood vessel ruptures, like the level of vitamin K and A in a chicken’s diet, fungal toxins, lighting programs, stress or even diseases like avian encephalomyelitis.
Some kinds of chickens are more susceptible to blood spots as well.
If your backyard chickens’ eggs seem prone to blood spots, make sure the chickens receive a good balance of vitamins, keep feed bins clean and free of mold, maintain proper lighting (not consistent, or in sporadic bursts) and follow a proper vaccination program.
“I think that one of the most important things a chicken owner can do is pay attention to nutrition,” Lichtenwalner said. “Your birds will compensate for nutritional deficiencies by continuing to lay but they will be drawing nutrients from their own tissue and putting them into the egg. You can have problems with bone density, feathering, irritability when chickens are compensating for a balanced diet.”
Lichtenwalner stipulated, though, that blood spots are one thing — blood diffused throughout the egg may be something else entirely.
“If you started having a lot of blood in the eggs, I would be very actively looking for causes,” Lichtenwalner said. “A spot is a normal event, no big deal, ignore it. Bunches of blood or a big smear of blood, that you should probably address. If you have a vet with which you work, contact them or contact us at [the University of Maine] Cooperative Extension. Perhaps you might have a problem with toxic substances in the environment of your barn.”
Another thing to look out for is a distinctive white bullseye shape in the yolk — that means the egg has been fertilized. They are still ok to eat — the embryo will not continue developing once the egg has been refrigerated — but they may not be for the faint of heart.
“Sometimes if you catch that really early right after the egg has been laid, you might find a tiny little bit of tissue,” Lichtenwalner said. “In some cultures, it’s considered ok and actually a delicacy to eat these eggs that have developing embryos in them.”
Most eggs with blood spots or other aberrations don’t find their way to supermarket shelves because they’re detected by candling — the process of putting a light behind an egg to spot any inconsistencies — or by more modern electronic spotters during processing and packing.
“Egg producers can spend a little extra time and candle their eggs to check for large blood or egg spots so their customers don’t have to deal with them,” said Donna Coffin, professor at the University of Maine Cooperative Extension. “Most customers are understanding, but some may want a refund or replacement if the blood or meat spots are large and unappetizing looking.”
The process isn’t perfect, though.
“Because that’s a light sensitive methodology, then birds that have a darker shell — it may not be quite as effective at detecting things like blood spots in those types of eggs,” Lichtenwalner said.
For the most part, though, small aberrations in your chicken eggs shouldn’t stop you from eating them, but keep an eye out for drastic changes in smell and texture of the yolk.
“If there’s something that really looks odd in an egg don’t eat it,” Lichtenwalner said. “If it smells weird, for sure don’t eat it.”