Lips go numb?stop sucking and ask them to leave with no refund. Cite possibly health risks associated with what they have rubbed on their cock. If they complain tell them you are going to contact the police. Thats disgusting. No one has the right to make you ingest a substance of which you are not aware and of which you do not have access to the advice leaflet. Id bet my left foot whatever he had on his cock had a note saying not to be ingested which he wouldn't have bothered reading as he didnt give a shit. How does he know you would not have an allergic reaction to whatever he has put on his cock.
This may seem a bit confrontational of me but hey, would a guy who does that hang around to help you if you had a respiratory reaction to what he has put on his cock?like hell would he, he would leave you to call 999 on your own and dump his sim card. What a wanker. You should put his number into a warning database as he could have had anything on his cock?coke being the least of someones worrys. Guys who do this sort of thing need to be classes as a dangerous punter because you had a burning mouth, the next girl may have breathing difficulties and end up in hospital, especially if she is on medication that has a reaction with whatever she gets in her mouth from his cock.