Legal Alien: A Scotsman in Montreal

QED II: A new hypothesis to test

OK, here it is - can your skin get used to the sun without it tanning? Being a Scot, I'm deathly white and when exposed to the sun I do a fantastic lobster impression. However, I have noticed that say if I'm on holiday somewhere sunny, after a few days of wearing sunscreen I can get away with not wearing any and not burning. However, my skin will have become red (as close to brown as I can get) but not sore. Is this because:

a) I have burnt my skin already a little and it doesn't react to the sun anymore i.e. you can't burn a sunburn?
b) Or has the melanin/melanonin/whatever-that-stuff-is in my skin ramped up its protection?
c) Or am I just talking crap?
d) Something else

I ask cos I raised the issue with a friend and she suggested that your skin gets more resistant. Of course, the skin always ends up peeling off after a couple of days which would maybe suggest a) is the answer.