A McDonald's diner claims she was nearly sick after biting into her McMuffin to discover the egg was "grey" and thought it was mouldy.
Kym Kirkham, 32, from Manchester, had treated herself to a McDonald's breakfast on Wednesday April 27.
But after taking her first bite of the sausage and egg McMuffin, the horrified teacher noticed the egg was "grey".
McDonald's has denied the egg was mouldy, saying it was impossible, and claimed it was instead a chemical reaction.
She said: "I only noticed after I'd taken a couple of bites. I was nearly sick.
"I don't recall the taste, I was too freaked out. I thought it was mouldy."
After taking the food back to staff at the Festival Park branch in Stoke on Trent, Kym claims staff threw away the McMuffin and offered her a new one.
But she said: "I couldn’t eat it though because I felt so sick after."
Since the incident, Kym claims she has been unable to report it to customer services.
But McDonald's has claimed that it is impossible for their eggs to be mouldy, adding that the grey egg is caused by a natural chemical reaction.
A spokesperson for the restaurant chain said: “At McDonald’s all the eggs we use across our breakfast menu are freshly cracked, cooked and served in a short space of time, meaning it is simply not possible for us to serve eggs that are mouldy.
"Discolouration when cooking eggs is caused by a natural reaction between the hydrogen sulphide in the egg white and the iron in the yolk.
“As soon as the customer made the restaurant aware that she was not happy with the product our team replaced it with another freshly prepared McMuffin.
"We are sorry that the customer was not satisfied and we’d encourage her to contact our Customer Services team.”
