Difference between parasite and meat spot in chicken egg
How can you tell the difference between a parasite, parasite egg, and meat spot inside a chicken egg? A couple of our chickens have dark spots/shapes in the white of the egg. I’m afraid to eat them.
I don't know of any parasite egg that would be in a chicken egg and that would be big enough for you to see. There are occasional reports of roundworms being in an egg, but those are usually visible (as a whitish worm - usually an inch or more long). There is also some information about a type of fluke that has occasionally been found in chicken eggs, but these are spread through dragonflies, so your hens would need to be eating dragonflies to be infected.
Meat or blood spots are certainly much more common, so it's likely that is what you are seeing. Hens that lay brown eggs can leave small flecks of pigment in the eggs, too. They usually look like little brown spots - sort of like pepper flakes.
I guess if they bother you, you don't need to eat those eggs (assuming they are pretty rare). If they are in a lot of the eggs, then I would guess they are pigment spots or meat spots. You can usually remove meat spots with a spoon fairly easily.