His revelation comes two days after his co-star Kaley Cuoco posted a photo on Instagram of herself and others sporting surgical masks on set, stating, "everyone at work is sick".
"Literally everyone is sick. We were rehearsing and we were doing scenes, and we were all wearing surgeon masks, doctor masks, because everyone was sick," Nayyar told Entertainment Tonight.
"I think, Mayim (Bialik) had it first, and then Kaley... Also everyone's got kids now. Simon (Helberg)'s got kids... Everyone's getting sick all the time. I think Mayim gets it from her kids, or Simon gets it from his. And they come to work and we're all hugging - we're all very close.
Things got so bad, the producers had to call in medics.
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"We had to bring the doctor to set, like, three times," he said.
But Nayyar, 34, credited his Indian roots with helping him stay healthy as his castmates suffer.
"I never get sick. It's because I'm from India, so I've seen every kind of bacteria you can imagine."
He said that Cuoco tries to keep him and the cast and crew healthy, when she's not so sick, by leading weekly yoga sessions.