The name Rengas actually refers to trees in the genera Gluta and Semecarpus. Here I refer the name to Gluta wallichii (I have been using this name to curse, and it really sounds like bad words). The Wallich's Rengas is actually quite common in our forest, especially at BTNR (70 big trees recorded in my survey), and they can grow quite big (the biggest Rengas I recorded is 78cm in diameter). However, we normally came across (and "kissed" by) saplings of our height. It is not difficult to spot them. Just look out for "black spots" (dried sap), just like those on mango skin.
Rengas' bark fissures like Seraya, but normally scattered with its infamous tell tale sign. Don't anyhow hug a "Seraya" if you are not sure what it is!
It's my laziness (of not wearing long) to be blamed for my rash, not Rengas. After all, at least we can spot a Rengas and avoid it, can't do that on ticks.
No matter what, I still love mango and cashew nuts.