Actress Emily Blunt accidentally gave an allergy breakout to co-actor Jamie Dornan while they were on the sets of their upcoming countryside film, Wild Mountain Thyme.

Both actors are allergic to farm animals and the film is set on a farm in Ireland. The two stars had to have a lot of "antihistamines" to avoid falling sick during shooting, reports aceshowbiz.com.

"Jamie Dornan and I are both wildly allergic to farm animals, so I feel like any scenes where we were with the animals, we were dozily wondering around on too much Benadryl (allergy medication)," Blunt said on the talk show "The View".

She added: "We were antihistamined up to our eyeballs at all points."

Blunt shared that she accidentally gave Dornan a reaction after trying to help him look his best during his close-ups, as she forgot she had been touching a horse.

"There was this scene where I'm holding the horse and I'm talking to Jamie, and I noticed this rogue eyebrow hair dropping down, right before his close-ups, and I said, 'Ooh, I'll just fix your eyebrow for you,' and then, within moments, his whole face had just turned into this red monobrow of hives! No amount of antihistamine is going to solve Jamie's hiving problem around horses," she said.

"It was absurd that we're playing farmers and we're wildly allergic to anything to do with a farm!" Blunt quipped.