Bowel cancer is the second most common cause of cancer deaths in the UK.
Symptoms include unexplained weight loss, extreme tiredness, a pain or lump in the tummy, and blood in your poo.
But, about 16 million people in the UK would either ignore blood left in the loo, write it off as something else, or just assume it will get better, according to the research by Red Trouser Day.
A third of 35 to 34 year olds ignore symptoms, the charity said, while only 10 per cent of over-55s ignore them.
Similarly, a third of young people were too scared to check for cancer symptoms, in case they find something. About 13 per cent of over-55s were too scared to check for symptoms.
Red Trouser Day founder Paul Finch said: “Bowel cancer is the fourth most common cancer in the UK, and is the second most common cause of cancer deaths in the UK.
“With early diagnosis, more than nine in 10 people will survive bowel cancer for five years or more, compared to one in 10 diagnosed with late stage bowel cancer.
“Catching bowel cancer early is vital but we need to be more aware of the symptoms.
“Be more open to discussing them with friends and family if you have concerns.”
If you find blood in your poo, you should see your GP, Finch said.
It may be caused by another health problem, as other bowel cancer symptoms could be, but it’s still worth checking out, he added.
It was vital the UK gets over the taboo of talking about cancer, he said.
Earlier diagnoses of bowel cancer will improve treatments and survive rates.
This year, Red Trouser Day is on October 19, and aims to raise money for bowel cancer prevention.
The money will be used to fund a new blood test for early detection of the cancer, and a project to assess how robotic surgery will improve bowel cancer care.
There are more than 40,000 new cases of bowel cancer in the UK every year, including more than 15,000 deaths.
Almost 60 per cent of patients survive the cancer, but Cancer Research UK said that over half of cases were preventable.