do you get tar? IMO tar itches the most because of its lesser refinement...which means it has several opiate alkaloids in it (codiene, morphine, thebaine, etc) in addition to heroin and its actually well documented that codiene-especially in higher doses- is usually the most itchy narcotic for most people.
There is also a certain cut that will produce extra itchiness so as to give off the impression that it's stronger dope. I can't remember which cut it is, but I've heard of it being used in conjunction with diphenhydramine(which helps kick in the nod) to fool the consumers
I personally have stopped using diphen with my dope because I started to notice my lungs getting wheezy and were taking on asthma characteristics. As soon as I stopped the diphen it instantly went away. which, I digress for a moment, but apparently a lot of chicago H snorting addicts are rushed to the ER for asthma attacks. The reason why it's seen a lot in chicago is because chi dope is notoriously cut with dormin(diphen). This actually happened to a friend of mine that fucks with the west side D (this is actually why he switched from snorting to the needle) and when he told me about it I got real paranoid cause I had just started noticing my lungs getting wheezy, etc. So let that be a warning to any dope sniffers out there that are noticing their lungs getting weaker; either start mainlining your shit or start getting raw...or else you're going to be in for an unpleasant surprise.
whew, I'm high.