One addict Louis interviewed explained that her latest delivery had “a smell to it” which meant that it had either been “re-cut” or was a “decent quality”.
Finding it hard to describe the vinegar scent, the addict offered her palm out to Louis to smell the drug.
As Louis explained that it was “weird” and moved his nose closer, viewers took to social media, with one tweeting: “Louis Theroux sniffing heroin off a woman’s palm is all I needed for my Sunday night.”
“Watching Louis Theroux sniff a bit of heroin has been the highlight of my week,” posted another, as a third added: “Watching Louis Theroux sniffing heroin is great Sunday tv.”
Louis himself tweeted: “Thanks for watching that, if you watched it, and thanks for your messages. Come back next week for sex trafficking in Houston. #DarkStates.”
In an interview with the Radio Times, he was asked if an addict’s description of the heroin high had ever left him tempted to try the drug himself, leading Louis to reply: “Yes. The smallest part of me.
“I never would,” he clarified. “But of course there is a little part of you that wants to know, to understand that rush.
“I wish, maybe, that a little had accidentally touched my nose,” he added. “Just to accidentally get an idea of how it feels.”
Louis did, however, explain that he certainly would never try heroin.
The second instalment of the documentary series will follow Louis as he explored the sex trade in Houston, Texas.
Trafficking Sex is set to take him on undercover operations with Vice police officers and examine how the city became a centre for people trafficking.
Episode three, Murder In Milwaukee, covers the increasing homicide rates in the city and will see Louis join Homicide division as they investigate some cases.
For help and information, phone the BBC Action Line on 0800 155 947, or visit bbc.co.uk/actionline.
Louis Theroux: Dark States continues next Sunday on BBC Two at 9pm.