Conan O'Brien's new slicked-back hairstyle was the result of treating a painful scalp sunburn.

After social media users questioned why the comedian, 63, had abandoned his trademark voluminous red hair, the television host and podcaster said the unexpected look came after following advice to rub oil into his scalp following an appearance at the opening of the Obama Presidential Center in Chicago.

Conan explained the story during an episode of his Conan O'Brien Needs a Friend podcast, with the former Late Night with Conan O'Brien, The Tonight Show and Conan host saying he developed a severe scalp sunburn last month.

Conan said his skull felt like it was "on fire" before becoming "really itchy" due to his sunburn.

He added: "Whenever I itch it, it looks like a snow globe. It looks like confetti - white freckled confetti is pouring off of my head. It's disgusting."

Conan explained because he has "so much hair" he had never considered his scalp could become badly sunburnt.

He said he was advised to apply oil to help the skin recover but forgot he was due to record his podcast with actor and comedian Molly Shannon.

Conan added: "I come in and I look like I'm in Sha Na Na. I'm a greaseball. I'm so greasy. I'm Frankie (Valli.)"

Continuing the joke, Conan compared himself to a 1950s street tough guy.

He added: "I look like I want to fight one of you in the parking lot by swinging a chain at you in 1952, or come at you with a switchblade.

"I really feel different. I just want to fight people on the street. I want to get a hot rod and drive it around."

He then referenced the 1978 musical Grease, saying: "I want to get Rizzo pregnant, so that Rizzo has a bun in the oven - you know what I mean?"

Still referring to the film, Conan added: "I'm one of the Thunderbirds that is easily 55 years old. I'm going to put a bubble-gum cigarette behind my ear."

Again calling himself a "greaseball", he said: "I'm just gonna keep rubbing oil into my head until this my skull heals."

Conan also praised Hillary Clinton for wearing what he described as a "giant" and "huge" hat at the event which left him suffering sunburn.

He added: "She's smart. She's laughing at me right now."

Photographs of Conan's noticeably slicked hairstyle quickly spread across social media earlier this week, with users comparing him to characters from The Sopranos and joking he resembled a used-car salesman.

Conan later reposted several of the comments on Instagram.

Among them were messages reading: "Who hosed down Conan?" and: "Seeing Conan's hair like this feels illegal."

Conan's distinctive hairstyle has long been one of his defining features.

Speaking to 60 Minutes in 2010, he joked that the towering quiff helped him stand out early in his television career.

At the time, he described it as "structurally sound" and added: "If there's an earthquake and you're in the Pacific Northwest, get under my hair."

Conan, who has enjoyed renewed success in recent years through his podcast and the travel series Conan O'Brien Must Go, also received widespread acclaim earlier this year after hosting the Academy Awards, with his performance prompting strong reviews and renewed attention on his decades-long career in comedy.