When the Weasley twins try to cross Dumbledore's Age Line to put their names into the Goblet of Fire, they are both thrown out after magically sprouting long white beards. Dumbledore walks in on them at this time.
"I did warn you," said a deep, amused voice, and everyone turned to see Professor Dumbledore coming out of the Great Hall. He surveyed Fred and George, his eyes twinkling. "I suggest you both go up to Madam Pomfrey. She is already tending to Miss Fawcett, of Ravenclaw, and Mr. Summers, of Hufflepuff, both of whom decided to age themselves up a little too. Though I must say, neither of their beards is anything like as fine as yours." (emphasis my own)
Harry Potter and the Goblet of Fire, Chapter 16: The Goblet of Fire
Dumbledore says that Fawcett and Summers haven't sprouted beards "anything like as fine as" the Weasley twins' beards.
Does that mean spells (and/or potions) affect different people differently?
I am aware Dumbledore might have just said that for comedic effect. But in the real world (out-of-universe), we know some people react differently to certain medicines, foods, etc. The reasons for this can be allergies or metabolism or something else (I'm not a medical practitioner by any stretch of the imagination so my knowledge on this is basically zero). But the cliché that every human is physically and mentally unique applies here. Does that even translate to magic folk? Can wizards be allergic to certain potions or maybe react differently to certain potions or spells?