Edward Connelly suffered from "badly inflamed eyes and a mild case of klieg eyes", prior to shooting his scenes looking into the studio lights. It took several days to recover.
It is clear that Renée Adorée used a double for Salome's dance. Adoree has no waist, but the dancer certainly does. Her back is to the camera for most of the dance, and when she turns around, her face is covered by her hands. The double was noted in Variety's 1927 review of the film.
When Lena refers to some of the showgirls as vampires, she of course means in the sultry seducer sense, not the blood-sucking sense.
The reptile was an iguana and not poisonous.