The "how many sick days should a person use" is sort of a personal pet peeve. I am a person who gets sick fairly easily (I've had migraines my whole life - diagnosed at 18 months old - and I have a few stomach conditions as well). I've often worked for people who never, ever, EVER get sick, never go to any sort of doctor's appointment (even general check-ups), and show open scorn and disdain for those who do. I can't tell you how often I was questioned on the necessity of a medical appointment (yeah, I know I could go to HR over that, but it wasn't worth it at the time) or told that I should come in and "work through it". At that job, I technically had 10 days of paid sick time, but I was not allowed to take it between October and March (our busiest times) - so when I fell incredibly ill in February, too bad. I had to come in anyway.
So, Dazi, I'm not sure what your point was in asking the question - whether you're on the sick-person side of things or the not-sick-person side of things, but my answer is "as much as the employer allows". If you get 10 days, you should be able to take 10 days without questioning from coworkers, supervisors, or anyone else.