Wrinkly eggs have a couple of causes. The first can just be the age of the chicken. It is not uncommon to see an egg or two that is wrinkly. Most of the time the eggs that follow are normal. If your chicken is young, it is as though the chicken is working out the kinks in the reproductive machinery. On the other hand, as a chicken ages, the albumen will become more watery. When the albumen is watery, it is more difficult for the chicken to wrap the shell around it and the yolk. Wrinkled shells can be a result.
Another frequent cause of wrinkly eggs is Infectious Bronchitis. Highly contagious, Coronavirus also called IB, is spread within the flock quickly. Chickens will cough, sneeze, rattle, and makes sounds like a baby with a bad cold. Chickens may even get watery eyes and seem droopy. IB damages respiratory, urinary, and gastrointestinal organs. The chickens will most likely recover from the virus, but will remain carriers of IB for the life. Wrinkled eggs may be all she lays from that point on.
Oh, and no worries, while the wrinkled eggs may look odd, they remain safe to eat as long as there are no cracks in the shell. I wonder what they would look like dyed?
There are lots of causes of odd eggs.
BONUS FREEBIE PRINTABLE: Alltech (specialists in animal nutrition and health) created a very informative poster showing common eggshell issues and lists possible causes. You can download a copy to print for future reference here.