Messi, the insatiable World Player of the Year, scored in each half at the Nou Camp to take his goal tally to 10 in the league this season as Barca cruised past toothless Racing to make it 17 points from seven games.
Real Madrid are a point back in second place after Messi's Argentina team-mate Higuain recorded his second consecutive La Liga treble.
Having scored three against Espanyol, he then repeated the feat against Chile on international duty last week.
"I'm very pleased. After having to wait so long to play, now I'm enjoying myself a lot," the 23-year-old told Spanish television, referring to the back injury that kept him out for much of last season when he lost his place to Karim Benzema.
"I wasn't playing a few weeks ago and I'm just making the most of my opportunities," Higuain added after his second-half hat-trick against Betis took his tally of league goals to eight this season.
France defender Adil Rami put Valencia ahead at Real Mallorca in the 39th minute but the visitors then conceded a stoppage-time penalty.
Tomer Hemed netted from the spot to earn new Mallorca coach Joaquin Caparros a point from his first match.
Struggling Villarreal and Getafe shared a goalless draw at the Coliseum while Atletico Madrid were held 0-0 at promoted Granada in the late game.
PIQUE INJURY
Barca made a poor start against Racing and lost defender Gerard Pique to a hamstring injury early on but Messi soon settled them down.
The Argentine combined with Andres Iniesta and snaked his way towards goal, fooling the visiting keeper before slotting the ball into an empty net from a tight angle in the 11th minute.
Midfield playmaker Xavi rose to head the second like a classic number nine in the 28th minute and second from bottom Racing, who have yet to win a game this season under coach Hector Cuper, had little to offer in response.
Messi sealed victory by firing in after Iniesta's shot came back off the post in the 68th minute.
Barca have now scored 21 goals without reply in their first four league games at the Nou Camp this term.
Promoted Betis made a feisty start at the Bernabeu but were torn apart by Real Madrid just after half-time.
Cristiano Ronaldo bore down on goal in the 46th minute and selflessly squared for Higuain to score into an empty net.
Ronaldo also helped set up the second goal when he fed Kaka in the area and the Brazilian curled a superb shot inside the far post.
Jorge Molina pulled one back for Betis in the 69th minute but any thoughts of a shock comeback were quickly extinguished when substitute Angel di Maria sent Higuain clear to round the keeper and make it 3-1.
Di Maria set up his Argentina team-mate again in the 73rd minute and Higuain produced a clever l
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