Finnish sources MTV3 and Turun Sanomat report that the Lotus driver was late for the pre-race driver parade because he was suffering from an allergic reaction.
"He gets it 3 or 4 times a year," the 2007 world champion's trainer Mark Arnall admitted.
"We have no idea where it came from just before the race, but it affects mainly his skin, and not so much his eyes."
Arnall said Raikkonen was treated with antihistamines.
Lotus engineer Alan Permane said: "Considering he (Raikkonen) was suffering before he started the race, it was a very impressive performance indeed."