That e-liquid is relatively slowly absorbed through skin is fortunate, because it gives time to wash it off (with soap). Nobody should think though that it will not be absorbed eventually, so always wash off even tiny amounts immediately. Same goes for surfaces, wipes, leaks, gloves, clothes, etc.
Cart leaks present the greater danger though and we do need better designs to avoid that possibility. Not having the liquid in the mouthpiece, and with the liquid 'sealed' (but refillable) such that only the expanded vapor can pass out through a valve or nozzle ...
If do get liquid in the mouth, spit it out as best as you can.
As with knives, power tools, electricity, drugs, cleaners, garden chemicals etc, respect the dangers and never get complacent. Don't take chances; that's how 'good drivers' get killed every day.
Right on, kin. This is to the people that are new to this DIY world. No matter the concentration, good habits make a healthy vaper. Respect the nic and it will be your friend. When I make DIY juices, everything is set up neat and orderly before I start, and then all my motions are very choreographed and controlled. I use a syringe for all dispensing, so I never touch the juice or have it drip accidentally from a dropper. In terms of dangers, I think it is a very good idea to wash your mouth out with water if you get nic juice in it from a cart. Swallowing a drop is not likely to give more than hiccups and a delayed big buzz. But too much nic hanging around in the mouth has been shown to make you lose teeth in the long term. 8-o This is common for very long term nic-gum chewers. Also, I have all my high-nic juices in glass bottles with eurodropper inserts, which allow for syringe needles to get juice out, but will not spill if knocked over. One thing about working with lots of nic is it is easy to get buzzed and clumsy.
Here is something to ponder: suppose you have a new jar of 75 mg juice. You want to make some juice. You are alone, and wearing shorts and t-shirt...or no shirt...maybe no shorts! You get careless and knock the jar over on you. Very possible to do when you are jazzed on your latest recipe. 200 mL gets all over you, the table, the floor, the carpet, your desk chair.
What do you do now? The clock is ticking fast.
Best to think out your plan of action for this horrible accident before it happens. Do no expect to think clearly if it does happen. As kin said, like anything else that is dangerous, respect the nic. In my setup, that scenario can only possibly happen once: when I transfer the juice to glass bottles with with eurodroppers for storage. After that, unless I drop and break a bottle, it can not happen...for months.
If you need to, practice transferring with water. These operations actually take a little skill. In fact I would like to see more threads here on safety in nic handling than there are. I've posted details of my DIY methods elsewhere on ECF.
Be safe, and live the longer life available to you now that you are vaping more and smoking less.