MACAULAY CULKIN’s tragic downward spiral continues – with the for­mer child star collapsing in public!

Just days after The ENQUIRER reported that eyewitnesses claimed the 31-year-old actor was hopelessly hooked on heroin, he was photo­graphed vomiting on the street – a sign that he could be suffering from heroin withdrawal, experts say.

Eyewitnesses have told The ENQUIRER that Culkin – who sky­rocketed to fame as the lovable tyke in the 1990 blockbuster “Home Alone” – shot heroin and the powerful pre­scription painkiller oxycodone.

After our shocking report, Culkin jetted from his home in New York to Los Angeles, sources say.

He was photographed outside the exclusive Chateau Marmont hotel on Aug. 3 wearing a heavy jacket and faded jeans, and appeared dishev­eled, according to an eyewitness.

Looking nauseated, Culkin stum­bled out of the hotel, and then leaned over and heaved into the ivy on the wall, said the source.

“Mac really looked like crap,” the eyewitness told The ENQUIRER. “He was clutching his stomach, made a face and then spit up – not once, but twice.

“He looked pale and sickly, and when he saw me watching him, he walked back toward the hotel en­trance. He jumped into a vehicle with some buddies and took off.”

According to medical experts, nau­sea and vomiting are among the symptoms of heroin withdrawal.

Dr. Elizabeth Waterman of Califor­nia’s Morningside Recovery center in Newport Beach – who has not treated Culkin – told The ENQUIRER: “Withdrawal symptoms typically begin between six and 12 hours after the last dose and can include nausea and vomit­ing, anxiety and depression.”

Two days after his stunning col­lapse, Culkin attended the wedding of his pal, actress Natalie Portman, in Big Sur. The bride starred in the movie “Black Swan” with Culkin’s former love Mila Kunis.

Sultry Mila, who’s now dating Ash­ton Kutcher, was not at Portman’s wedding.

“Mila was the love of Mac’s life, but she dumped him over his drug use,” a friend told The ENQUIRER. “She just went on a romantic trip to Bali with Ashton, and that destroyed Mac.”

As The ENQUIRER reported in its blockbuster story, pals blame Culkin’s stalled career – he hasn’t had a hit movie in years, and per­forms as a DJ at small clubs – and his failed eight-year romance with Kunis, which ended in 2010, for his downward spiral.

The troubled actor nearly overdosed several months ago according to in­siders and has spent up to $6,000 a month on the dangerous painkillers Percocet and Vicodin, sources have told The ENQUIRER. Friends fear that if he doesn’t get profes­sional help, he could be dead within six months.

Culkin’s rep blasted The ENQUIRER report as “without merit,” but the heartbreaking news of his drug woes has generated an outpour­ing of concern.

Former child ac­tor Paul Peterson, star of “The Donna Reed Show,” urged Culkin to seek help at his nonprofit foundation, A Minor Consideration.

“We’ve worked with more than 600 child stars whose careers have evaporated,” Peterson told The ENQUIRER.

“Mac needs to know that he is not alone, and we can get him help.”

The ENQUIRER also issued a statement advising the actor to seek professional counseling, but sources close to Culkin fear he’s beyond help.

“Mac’s problem is that he pretends nothing is wrong,” his friend told The ENQUIRER.

“After The ENQUIRER exposed his secret life, he fled to Los Angeles, and I believe he collapsed due to her­oin withdrawal. But partying in L.A. is the last thing Mac should be doing. He should be in rehab, and we fear that if he doesn’t get help, something tragic will happen.”

 ‘Home Alone’ star suffering from heroin withdrawal symptoms after being exposed in ENQUIRER

– say friends

The actress looked like a homeless wino as she drank and threw up at a Studio City, Calif., park on Aug. 4