The actress was supposed to walk the red carpet prior to the 2012 Academy Awards, but shortly before the show she tweeted that she had taken ill.
"bailed out of #oscar festivities 2nite due to this terrible illness (sic)," Alba wrote.
Alba recently advised Beyoncé and Jay-Z to sell the first pictures of their baby girl Blue Ivy Carter.
The 30-year-old has said that her daughter Honor loves to dress in drag, saying that she refuses to listen to fashion advice.
The 84th Academy Awards continue on ABC in the US and Sky Movies in the UK.