The easiest thing to do, particularly if you move to DIY, is to start with UNFLAVORED juice, maybe even 100% VG and VG nic base with DW added, and go from there. Try a flavoring at a time, then you can mix them later.
Note: Not all VG is created equal, and can be a concern too. It is made from various sources, palm, veg, and sometimes coconut. So consider your sourcing. I've had some that cause hives, and most that didn't. But that was years ago, and the industry may have moved to other sources of VG.
Also RY4's often contain nut flavors. That's not peanut proteins, but it may be a factor for you depending on the nature of your allergic reaction.
And keep an epi-pen if you have known allergies if you can.
Note: Not all VG is created equal, and can be a concern too. It is made from various sources, palm, veg, and sometimes coconut. So consider your sourcing. I've had some that cause hives, and most that didn't. But that was years ago, and the industry may have moved to other sources of VG.
Also RY4's often contain nut flavors. That's not peanut proteins, but it may be a factor for you depending on the nature of your allergic reaction.
And keep an epi-pen if you have known allergies if you can.