There is a range of opinions on this subject however from personal experience I often get a drop of milky sap in my mouth or eye when pruning a high frangipani branch. To be on the safe side, I always wash my eye or mouth out with water. Having said that, the taste is not too bad and I’ve never felt sick afterwards.
When cutting off numerous high frangipani branches, I often get sap run all down my arms. If I keep working a few hours, when I take a shower later, I find the sap has dried like glue and it’s very difficult to get off with just soap and water.
If you wash the frangipani sap off your skin with water before it dries, it comes off easily. Sometimes I’m too busy or there is no nearby tap so spreading it out and rubbing it into the skin makes it easy to wash later