Not sure but my daughter gets this. If she gets cold (even when it's not really cold), her lips turn blue, also when she runs about etc. Anyway took her to the doctors and they checked her over and said unless she's limp or sleepy when it happens not to worry. I'm not entirely convinced but hey ho. They say it's your heart or circulation when your lips turn blue so maybe just see your doctor just to get checked out. Like I say my daughter's been like this since birth and the doc isn't worried x