The award-winning British actress, known for playing Queen Elizabeth II in the hit Netflix royal drama, said she thinks she contracted the bug in Morocco.

Speaking on the Table Manners podcast with Jessie and Lennie Ware, Foy explained: “Quite a few years ago, I had parasites. Gross.

“I kept losing weight and I didn’t know what was going on. They travel as a pair. I got told by the doctor, gross, absolutely rank. It’s disgusting.”

The 41-year-old went on to explain that she had to make changes to her diet, including ditching caffeine – as part of a parasite cleanse – because she “didn’t want to take really hardcore antibiotics”.

“I took all this little gross stuff, and part of that was giving up caffeine,” said the star, who is also known for BBC historical drama Wolf Hall and A Very British Scandal.

Asked how long she thought she had parasites for, Foy replied: “At least five years.”

Revealing more about her gut health and dietary needs, Foy said she had also dramatically cut down on eating gluten or sugar in order to help manage a separate autoimmune condition.

“This is my big secret, I feel like I’m in The Traitors or something, and I’m letting everyone know that I’m related to someone,” she joked.

“I don’t actually eat gluten or sugar… except when I go out for dinner. It doesn’t have an impact on me. It’s just because I have an autoimmune condition, so I should avoid anything which causes more inflammation.”

Foy won two Emmy awards and a Golden Globe for her portrayal of the late Queen, and also starred in the 2022 film Women Talking and the new screen adaptation of H Is For Hawk.

The actress is set to appear in two more forthcoming films: Enid Blyton fantasy The Magic Faraway Tree, and the black comedy Savage House, opposite Richard E Grant.

Last month, she told the Sunday Times that when she was younger, she thought she would “never make it past 40” due to “many medical things in my life”.