Krokodil is an underground narcotic that possesses a nasty side effect: It causes users' flesh to rot. Its use has been mostly confined to Russia, although authorities believe the synthetic opiate has recently hit Western Europe after reports of customers with "disastrous" skin deformities showing up in German drug cafés. Here, a brief guide to the drug and its stomach-churning side effects:

Why is it called krokodil?
Quite simply, it earns "its reptilian nickname by turning users' skin scaly," says CNN, "eating them from the inside, and rotting the brain and limbs, before precipitating a painful death." Graphic videos can be found all over YouTube, highlighting krokodil users' gory symptoms, which include gangrene, infections, and sores open all the way to the bone.

What is it made of?
It's a cocktail made by mixing codeine, benzine, paint thinner, hydrochloric acid, and red phosphorus. It's the hydrochloric acid that causes "the eventual destruction of the skin," says Keith Veronese at io9. One reason for the drug's prevalence is that it can be cooked up cheaply in a homemade kitchen — no fancy lab required. Producers often substitute ingredients (like using gasoline as a solvent, or getting phosphorous from the striking surface on matchboxes), which further impurifies the mixture and sickens users.

Why is it so addictive?
Krokodil is an extremely cheap alternative to a heroin high, says Veronese. It's just $6 to $8 per injection — compared with $150 for heroin. And its active ingredient, desomorphine, "is 8-10 times more potent" than morphine (which is used in heroin). Users who try to quit typically experience painful withdrawals, with success requiring a "phenomenal amount of willpower"; krokodil junkies typically live just three years after starting, with many dying within their first year.

Why is it so prevalent in Russia?
Two reasons: First, its essential ingredient, codeine, is available in Russia without a prescription. Codeine pills in particular are widely available, and can be cooked into krokodil in a half-hour. Second, the rehab system in Russia is essentially nonexistent, leaving users crippled under the weight of their own addictions. The drug's use is so widespread the amount of krokodil seized in the country has "increased 23-fold" since 2009, and in some regions it has even "pushed out traditional opiates."

Sources: CNN, io9TIME, World Crunch