Kentucky Derby winner California Chrome has a small blister in his throat but is reported to be fine as he prepares to run in Saturday's Preakness Stakes.

California Chrome coughed about four times on Thursday after galloping, according to Alexis Garske, spokeswoman for Sherman Racing.

Trainer Art Sherman and his son and assistant, Alan, had a veterinarian check California Chrome and draw blood, and the blood work came back "100 per cent clear," with no infection present, Garske said.

The small blister is being treated with glycerin throat wash and is not expected to affect his preparation or performance in the Preakness for which he is the 3-5 favourite.

"The horse is fine, it's not like he's coughing a lot and it's just because it itches him," Garske said.

"The thing with Chrome is he actually coughs every morning a couple of times. The only reason (for the vet check) was because the coughs were closer together, so they figured let's get the vet over here just to be sure especially with the temperature change (in the weather).

"But he actually coughs quite often."

Alan Sherman added that California Chrome had the blister going into the Kentucky Derby before his dominant victory.

"He had it and it went away," Alan Sherman said. "After he ran it came back a little bit, but it's not a big deal at all. I don't know how they get them (blisters) but a lot of horses get them."