After eight years as US President, Barack Obama might have gained a few grey hairs, but his hairline remains as robust as ever.

Many people on social media have commented that they are amazed that despite having the most stressful job in the world, his mane has managed to break through virtually unscathed.

While this is in part down to genetics, the man who has been Barack Obama’s barber for almost 20 years has to be afforded some credit.

Known only as Zariff, the Chicago native has worked at Hyde Park Hair Salon, a barbershop that has trimmed the hair of everyone from Muhammad Ali to Spike Lee, ever since graduating from school and has served as the First Barber of the United States, or FBOTUS, for the past eight years.

So, what is the secret to Obama’s enduring hairline?

“Once you find a good barber you keep your barber. There’s a good reason why I am his barber,” Zariff told Complex.

“There might be a flaw or two in his hair, but it’s all in the technique, it’s all in the lining and how you present that.

Zariff has been Barack Obama's barber for almost 20 years (AFP/Getty Images) (AFP/Getty)

“I don’t believe in razor lines. Razors are so harsh they give you a very sharp and defined line, but they take away a lot on the hairline, the top layer of the skin, everything, because you are trying to get that line so defined. Keep a natural line with electric liners.”

As you would expect, Obama has become a cherished guest at Hyde Park Hair Salon but Zariff was keen to assert that when visiting the shop, he acts just like any other customer.

“He would definitely participate in all the debates when he was there. He’d get on your case too. He was very intelligent, but he didn’t really throw it at you. He would lay back in the cut with it and listen to everybody else.”

As Obama steps aside, Zariff recalled some of his favourite moments.

“It’s a really simple one: When he used to bring his girls in the shop every now and then when they were very young,” he explained.

“Of course, they were so little they’d sit in the chair and their feet wouldn’t even hit the floor.