Is oral thrush by any circumstances dangerous?

Not usually. Not usually. It can be a sign of a more serious problem like diabetes or an immune system problem. In healthy adults, it is usually caused by antibiotics or medicines (steroids).
Can be. in and of itself it is not usually a serious illness, but if recurrent it can be a sign of some serious illnesses like diabetes, HIV, and as such can be important. it can follow the use of antibiotics as well. if severe enough, it can make swallowing difficult and result in dry mouth, dehydration and choking on secretions. it should be treated early and aggressively.