The Block's Lysandra shares emotional warning to parents beside her son's hospital bed.

The Block star Lysandra Fraser has warned parents about the dangers of ignoring their children’s symptoms after her son was hospitalised.

Fraser told fans that her seven-year-old son Emerson had contracted croup, an upper airway infection that causes coughing, in a post to Instagram on Monday.

The mum-of-two, who appeared on the Channel Nine TV series with her twin sister Alisa in 2013, said she decided to share the awful news in a bid to help others.

Listen: How visiting someone in hospital can mean the world for the family. (Post continues…)

“It’s often a fine line deciding what we choose to share about our lives on social media. A lot we keep private and a lot we choose to share,” Fraser wrote.

“This one I’m deciding to share, not because I want everyone to know that Emerson is in hospital with croup, but because I was naive and thought that it was only babies and toddlers that suffered from severe cases of it.”

Fraser said she thought her sons Emerson and five-year-old Cohen were “past the danger age” of contracting the virus and ignored symptoms her son displayed.

A post shared by Alisa & Lysandra • Interiors (@alisa_lysandra) on Feb 27, 2017 at 2:34am PST

“I ignored my generally strong instincts, passing it off as just a common cold. At 3am Emerson woke up with a nasty cough and he was struggling to take in any air.

“He was taken to hospital by ambulance and 18 hours later we are still here while they monitor him closely.”

Anticipating backlash for the post, Fraser said she knew “a lot of people might think that I am stupid and naive” for thinking that older children couldn’t develop croup.

“But for those who were under the same belief as me, I just want to let you know that it is certainly not the case. Trust your instincts, I wish I had a bit earlier.”

A post shared by Alisa & Lysandra • Interiors (@alisa_lysandra) on Feb 1, 2017 at 2:46pm PST

However, commenters were kind to the mum, aged in her early 30s, with messages of support and encouragement.

“Don’t be hard on yourself! I still have trouble deciding what’s croup and what’s his bad cough and he gets it every year!” wrote one mum.

“Poor guy. Hugs mumma bear. You did nothing wrong and got him the help he needed when he needed it. Hope you get to go home soon,” commented another follower.

We’re sending thoughts and positive energy your way, Emerson!