Why I give my four-year-old daughter Viagra

Ruby Ernest is just four years old, but she has already spent many long nights in hospital, struggling to breathe as the inoperable tumour in her lung swells.

Six months after doctors told Ruby's family that there was nothing they could do, help came from an unexpected place: a packet of tiny blue pills traditionally used to treat erectile dysfunction.

For the past five weeks, Ruby has been taking Viagra every day as part of an experimental drug trial in conjunction with Stanford University in the US.

Researchers are hoping the controversial treatment will shrink Ruby's 9.5cm lymphatic malformation, a tumour-like deformity that is blocking her airways and putting pressure on her heart.

Ruby's mother Jo has been hoping for a cure ever since the tumour was discovered in March, but admits she was a little dubious when the paediatrician suggested Viagra could help.

Her disbelief was quickly replaced by excitement, but many of her family and friends have been unable to get past the bad jokes.

"It's been shocking!" Jo says. "Even the doctor has been throwing erection jokes around!

"My dad is an absolute shocker! A lot of people don't seem to know whether they should laugh or look concerned, so I've been breaking the ice.

"I say, 'How ironic is this? We're using Viagra to make something smaller?'"

Ruby is now nearly half-way through the recommended 12-week trial. Doctors are yet to see any noticeable results, but shrinkage is not expected until week 11 or 12.

Jo hopes the medication will do its job, but she's trying not to get her hopes up.

"I can't think about the future because then I can't cope," she says. "You just have to take things one day at a time. It's a roller coaster of emotion. I'm grateful for hair colour because I've literally gone grey overnight.

"The tumour is touching her heart already. Tomorrow it could grow, could swell in the wrong direction and that could be it.

"That's the hardest part — the unpredictability. There's this ticking time bomb inside your baby and you don't know when it's going to go off."

Sadly, Ruby's condition is likely to worsen as she gets older. Lymphatic malformations grow with the child, swelling larger every month.

Until recently, the condition has been considered untreatable, as the enlarged lymph vessels are too close to vital organs to remove them surgically.

But earlier this year, doctors at Packard Children's Hospital in San Francisco discovered a potential cure while treating a child with an unrelated condition.

The patient — who coincidentally suffered from severe lymphatic malformations — was given Viagra to treat pulmonary hypertension, and doctors were shocked to discover the drug shrank the girl's tumours significantly.

The findings were published in the New England Journal of Medicine in January and Stanford University is now closely following the treatment of other children around the world with the condition.

If you want to show your support for Jo and Ruby, join their toy challenge and donate toys to public hospitals who desperately need them.