Buddy's truck need advice please

[AverageJoe]

I'm trying to help my friend who possesses no knowledge of vehicles. (nice way to put it). Im no mechanic But i know something's wrong. His truck is a 91 350 tbi and is losing antifreeze everytime he drives it. I watched under the truck and there is no leaks anywhere (besides a little oil).It loses about a quart on short trips. I pulled the dipstick after the truck had been run and there was little bubbles on it and milky at the bottom. I let the truck cool and checked again and the dipstick had milky swirls all the way up. I assumed maybe a small headgasket problem? Could it be anything else? I know these trucks can build up condensation from sitting, but it only sat for two weeks and it hasnt cleared up in the past few days of driving. Thanks, truck runs perfect too.