Poppers were originally amyl nitrite, but that's now available only as a regulated medicine.
Next came butyl nitrite, which was outlawed in 2006.
This has left us with the rather rubbish isopropyl nitrite that you buy nowadays. Little effect, but make you feel like crap afterwards. And, particularly gallingly, the eyesight risks are associated with isopropyl nitrite, rather than its predecessors.
Poppers were to be included in the ban on legal highs, but were excluded after some strong campaigning.
Just a shame that we're stuck with the crap that is sold in the UK...