Whenever I write a number on my hand I’ve been lectured about getting cancer from the ink. Is there any truth to this?
Well, maybe, if the ink is radioactive. AFAIK, general use inks are pretty non-toxic. I wouldn’t recommend drinking it though.
From this site;
Hope that makes you feel better. 
Are the people lecturing you wearing tin foil hats by any chance?
The odds are statistically the same as getting mono from riding a monorail.
Interesting! I’ve never heard the idea that you’d get cancer from ink.
What I was always told is that you’d get “ink poisoning” from writing on your hand; these folks weigh in on the topic, and the answer seems to be, “You’re probably not going to drop dead two seconds after the ballpoint pen touches your skin, but it’s not all that great for you, so why not err on the side of caution?”
But…how can I ever remember anything if I’m not allowed to scribble handy ( ) reminders down?
WAG
Of coures you will if you write/print the word “CANCER” on your hand!
You’re probably safe as long as you don’t make a habit of it. And I wouldn’t go licking the ink off unless it specifically says “non-toxic”. From what I can tell with a bit of research, ballpoint and felt tip ink pigments seem mostly harmless but in order to get them to be non-smeary, they are often suspended in some volatile organic solvents (especially the eraseable inks). The links I found weren’t very forthcoming about what the solvents are, but it’s generally a good idea to avoid prolonged contact with volatile organic solvents. (Although the solvents in ink may just be alcohol – a volatile organic solvent a lot of people spend a lot of time in contact with. )
[speculation] It would not surprise me very much if the * original * ballpoint inks from the 1940’s contained stuff that’s now considered hazardous, e.g. benzene or carbon tetrachloride. So it may have been the case that in the past, writing on your hand would have been a less wise option than nowadays.
You can see the Material Safety Data Sheets (MSDS) for Sharpie inks here. According to those, their inks do not contain any known carcinogens.
I bet they’re high school students. It’s almost worse! 
Ink on your hands, no.
Ink in your pipe, possibly.
I have quite a bit of ink permantly lodged in the dermis layer of my skin. So far I seem to be okay.
Woo hoo, no cancer! I sometimes trace the lines on my palm during school when I get really bored and I’ve been told off by a lot of teachers. Most of them were around in the 40s (or the stone age, for that matter) and probably think the inks used then are still used now. I’m so printing this thread out.