Note Shannon has since tweeted about this saying "Thanks for asking,Gene is fine,he was just tired & dehydrated fr TRYING 2 beat me in the Rally4Kidswith Cancer! Vacation is not his thing."

From TMZ:
Gene Simmons was spotted leaving Centinela Hospital in Inglewood, Calif. today after he fainted at LAX yesterday. Sources close to Simmons tell TMZ he hit his head after fainting and was rushed to the hospital. He suffered a cut on his forehead and, after tests were run, sources tell us the doctors concluded it was just dehydration.

He was released today. We actually got Gene out Saturday night and he was in good spirits

Full story over at TMZ here.