At least 49 people have died in the Siberian city of Irkutsk after drinking bath essence, Russian authorities say.
The hawthorn-scented liquid was consumed as if it were alcohol, according to Russia's Investigative Committee.
Several others are in a serious condition. Several people have been detained over the deaths and police are removing bottles from shops.
Investigators said a warning that it should not be swallowed was ignored.
The product, called Boyaryshnik (Hawthorn), was found to contain methanol, a toxin found in antifreeze. A state of emergency has been declared in Irkutsk, and Russia's top investigative agency opened an enquiry into the incident.
Police uncovered an illicit workshop where the lotion was being made, and arrested its owners.
Russian media reported that the victims were poor people, aged between 35 and 50, and were not drinking together.
Household products are seen by some as a cheap alternative to alcohol across the former Soviet Union.
Two years of Western economic sanctions have made the situation worse, and analysts say up to 12 million Russians drink cheap surrogate alcohol, including perfume, after shave, anti-freeze and window cleaner.
While poisoning from alcohol is common, this is one of the deadliest incidents in years. This, officials said, was because the ethyl alcohol which was normally present in this product had been replaced by methanol.
A local official told Tass news agency that the liquid came in bottles whose labels said the content was 93% spirit.
President Vladimir Putin's spokesman described the case as a "terrible tragedy".
And Prime Minister Dmitry Medvedev told a cabinet meeting that authorities need to ban such substances quickly. "It's an outrage, and we need to put an end to this," he said in televised remarks.
Last month, Russia's Deputy Prime Minister Alexander Khloponin said medicines and perfumes accounted for up to 20% of the alcohol drunk in the country.