I made about this same post 10 months ago asking the question "is Riskee risky?", and now I am stating it rather than asking. For me, Riskee/Ruyan #4 causes infected taste buds if vaped for more than 2 days in a row. An infected taste bud is when just one taste bud swells, turns red/white, and causes great pain on your tongue. My mother used to call them "lie bumps". You also might be familiar with then from eating too much acidic citrus-based fruits like lemons or pineapples. I have done my own little study with this juice and I have gotten the same results for 6 months straight after I made the connection. This has not occurred with any of the other juices I use. After 2 days of just Riskee/Ruyan #4, I will get at least one infected taste bud. If I do not switch juices, the infection continues and spreads to other taste buds. When I do switch to another juice, the infection begins to heal and go away. Riskee/Ruyan #4 is my favorite flavor juice and even though the infection is painful, I will not give it up. I just use it in moderation. If this has happened to you, please share. It could be that I am allergic to an ingredient and thus not a concern for most of the vaping population. Thanks!