But while many criticized Irmelin for her unshaven underarms, branding it ‘gross’ or ‘disgusting’, others have jumped to the defense of Leo’s mother.

History in Pictures posted this carefree picture of the DiCaprios with the caption ‘Baby Leonardo DiCaprio with his mom and dad, 1976’

Lukas Ikceinezrok posted: ‘WTF is that under her arms?’

Alex Bratcher said: ‘It was the 1970s, not the 1400s.. Women shaved their armpits then. It’s obvious his parents were hippies…’

Eric Arsenault posted: ‘Women with hair under their arms is f***ing disgusting’, while Jude Lopez agreed added: ‘Women with hairy pits are gross.

‘Women should know better. I shave parts of my body to please women. They should do the same. Well, they don’t have to if their butch feminist girlfriend doesn’t mind.’

Thousands hit back at the negative comments, defending Irmelin’s hairy armpits as ‘natural.’

Trisha Dowd said: ‘It’s so funny I am part of a generation that wants to “free the nipple”, but freaks out when women have hair in their armpits. #feminism.

Irmelin, who has not responded publicly to the debate, accompanied her son to the Oscars where he won Best Actor

Facebook users commented quickly on Irmelin’s underarm hair, calling it ‘disgusting’ but many women and men pointed out that shouldn’t be what people focus on  because it’s ‘natural’

Kalea Kiesser added: ‘Why does his mom have to shave? All women grow hair under their arms. This was a different time. This was normal. And women STILL DONT have to shave to appease you! She’s not gross.’

Wesley Weyandt said : ‘I guess some of these guys didn’t know women grew hair on their armpits. Get over it.’

Others were disappointed that one woman’s hairy armpits were such a big topic of debate.

Sara Maccini said: ‘When i saw this, I thought “Wow, that little toddler just got an Oscar. His parents must be extremely proud!” Not “Omg, his mom didn’t shave her pits during a time where women didn’t shave their pits.”‘

Amanda Ziegler wrote: ‘If you actually care if a woman shaves her pits or not and that’s what you choose to comment on instead of her actual beauty or this lovely family picture or that Leo won an Oscar, you’re an awful human being.

‘Hair grows there, it’s natural, get over it.’

Key Lynn posted it was a sign of the times as it was common for women to choose not to shave in the 1970s.

Jeanette Casto addde: ‘His mother was the one that worked multiple jobs to support her and Leo… and all the ignorant comments about her armpits.’

Leo is close to his mother and has taken her as his date to awards shows numerous times (pictured together at the What’s Eating Gilbert Grape Premiere in 1993, left, and the 71st Annual Golden Globe Awards, right)

The actor won his first Oscar last week for The Revenant and mother Irmelin and father George, who have been separated for years, both attended the awards

The picture was posted with the caption ‘Baby Leonardo DiCaprio with his mom and dad, 1976.’

Irmelin has not reacted publicly to the debate.

The proud 73-year-old recently appeared alongside her son at the Oscars to see Leo finally take home a statue for his performance in The Revenant.

They pair, who are extremely close, were joined by his rarely-seen father George DiCaprio – and their respective partners – for a unique family reunion.

The parents, who met at a college in New York City in 1965, have been separated since Leo was born in 1974 after financial woes put a strain on their relationship.

But despite living in one of the roughest neighborhoods in Hollywood, surrounded by prostitution rings and 𝑠e𝑥 shops, they were both determined to give their son a wholesome upbringing – so they lived in adjacent houses with a shared garden.

Irmelin is not the first high profile woman to challenge the stereotype that women must shave their underarms.

Julia Roberts, 48, famously showed off her armpit hair in a sleeveless dress at the premiere of Notting Hill in 1999.

Many women were outraged by the focus on Irmelin’s body hair and commenters posted it was common in the Seventies not to shave

Both Miley Cyrus and Julia Roberts have previously shown off their unshaven underarms

More recently, Miley Cyrus, 22, was seen rocking a bushy underarm region on Instagram and at red carpet events.

Scout Willis, the 24-year-old daughter of Demi Moore and Bruce Willis, has also showed off her dark armpit hair on a number of occasions.

It comes as a growing number of women eschew their razors in favour of going au naturel.

A crop of Instagram pages have sprung up in recent years to celebrate women who refuse to shave their underarm hair.

The popular accounts post photos of women showing off their armpits in all their unshaven glory.

The latest addition, Armpit Museum  posts images of women with their arms held high, proudly showing off wisps of hair – some even dyed in bright colours.

Commenting on the trend last summer, Refinery29’s beauty editor Maria Del Russo said: ‘I think the reason more and more women are using social media to show off their body hair choices is connectedness.

‘Since the idea of women having body hair is not considered the “norm,” women who feel that it is their norm are likely attempting to make connections with other women who feel the same way.

‘What one woman decides to do with her body hair is her business, and hers alone. For plenty of women, it’s just hair.’

WHY DID WOMEN START SHAVING THEIR ARMPITS?

Today, female body hair is mostly considered a no-no in American culture, with women shaving, waxing, and even using laser removal to make sure their skin is completely smooth. But of course, things weren’t always this way.

The majority of US women did not shave their armpits until 1915, when sleeveless dresses became a socially acceptable trend – after a series of 𝑠e𝑥ist ads.

Culture: Advertising told women that underarm hair was something they should be embarrassed of

In the spring of 1915, Harper’s Bazaar published an article telling women that ‘sleeveless dresses and modern dancing’ have made it necessary to remove ‘objectionable’ underarm hair.

A slew of anti-armpit hair advertisements followed, with shaving and deodorant companies portraying women 𝑠e𝑥ily showing off their bare underarms in magazines.

One ad for the deodorant brand Veto sees a woman holding her arms above her head as a man lies on top of her, along with the tagline: ‘Because you are the very air he breathes.’

Another magazine advertisement, titled ‘Without embarrassment: An intimate talk to women’, shows a woman in a sleeveless dress proudly flaunting her bare armpits.

‘The fastidious woman today must have immaculate underarms if she is to be unembarrassed,’ reads the subtext.

Eventually, the trend took hold, and women began feel self-conscious about their underarm hair and shaving their armpits.

A century later, underarm hair is still for the most part considered unseemly in American culture, although there have been some women who are trying to disrupt the trend.

In predominantly Muslim countries, such as Turkey, men and women are required to remove their underarm hair in order to comply with Islamic cleanliness guidelines, whereas in China, women only began removing their underarm hair within the past 20 years.

Despite the jokes about French women having hairy armpits, the country’s women, like those in most of Western Europe, tend to keep their underarms bare.