I'm just passing by, I agree with Iminawe
If the q-tips are intact, that's probably not from heroin use... Most people take the cotton off the ends of the q-tips to use as a filter when filling up a syringe, so unless the cotton is missing, or you find the cotton all wadded up and wet, I highly doubt it's being used for shooting heroin.
No clue about the qtips, but you could always buy an OTC drug test kit if you think he'll take it and if he's not hiding anything why wouldn't he?