It can range in severity from "just a small leak" to complete loss of bladder or bowel control. Sneezing and coughing are common triggers and it usually affects women after giving birth.
More than half of those affected are aged 50 and over and 80 per cent of sufferers are women.
It's more prevalent than asthma (more than 2 million), anxiety disorders (2.3
million) and arthritis (3.1 million), but incontinence is usually discussed in hushed tones among close friends.
This week is World Continence Week and the Continence Foundation of Australia has released shocking new findings showing just how bad the problem is.
The national health survey found that 8 in 10 Australian women affected by bladder leakage fail to seek help for the problem, with 72 per cent preferring to "laugh off" the issue.
More than three quarters of those surveyed knew pelvic floor muscle exercises could prevent or improve incontinence, but just two per cent performed their exercises the recommended three times a day.
But after her two incidents, Alice realised she needed to do something.
"I only had two episodes, but that was two episodes too many," she said.
"I wanted to catch it before it interfered with my quality of life. I didn't want to be the one sitting in the corner at the wedding, afraid to dance. I love running and I wasn't prepared to give that up. That would have changed who I am and really affected my mental health."
She now performs exercises everyday to main her pelvic floor muscles and has gotten back into running.
"I haven't had any other issues," she said.
While women over 50 are most likely to be affected by incontinence, young women without children are not immune.
A 2011 study from Monash University found one in eight women aged between 16 and 30 who hadn't had babies had some form of leakage.
Continence and women's health specialist Dr Margaret Sherburn, from The University of Melbourne, says young women are often embarrassed or unsure how to treat the issue, so they simply make do.
"They normalise it and that can be dangerous, because once it's normalised you don't seek treatment," Dr Sherburn said.
"It's not a serious leakage, it's not a huge amount, but it's enough to say 'I must go to the toilet now'. But your normality can shift over time gradually and the condition gets worse.
"It can get to the point where they can't get through a movie or a show or a dinner out without popping off to the bathroom."
Dr Sherburn says all women should be performing daily pelvic floor exercises. Those with incontinence issues should seek professional treatment and request a tailored exercise plan.
"People say 'I do the squeeze exercises at the traffic lights', but really are you doing it that hard? A few minutes of concentrated work is better than 20 half-hearted ones.
"Even 3-10 repetitions a day of really high quality, concentrated exercises makes a difference."
While the physical impacts are obvious, the mental health ramifications are concerning, Dr Sherburn said.
"If you are young and you leak, it really does impact your self esteem. Even if it's only a little bit of leakage, if it's impacting your confidence, then that's a really clear signal to get help," she said.
"When people are constantly thinking about where the next toilet is, that's gone past normality. It's impacting on their life. They need to get help."
