I've had this conversation a time or two with my eldest, who used to play and scream in a heavy metal band, but now does folk in my band. He would never listen until he started doing folk and realized people were actually listening to his singing. Two things to keep in mind: 1) your vocal chords are very specialized muscles, and can be ripped and torn like any other muscle; and 2) things you put down your throat will not directly affect the vocal chords because they are not in the throat. However, the irritation you sense may truly be in the throat and they may help in that case. My sense of most rock vocal styles is that they are "all in the throat" and generally lack good diaphragmatic support. The fellah who used to sing with us swore by whiskey or whisky (they are two different things)and would be sipping the stuff in medicinal quantities throughout a gig. We're not talking about getting sloshed here, but enough to be psychologically and. perhaps, physiologically relaxed. It worked alright for him, but he also had good breath support. Guinness works as well for me. The bottom line is that you will most likely screw up your voice for good if you stay in that genre. The best advise has already been given - get out NOW!