Charlie Rowley, a British man who was poisoned by a military-grade nerve agent in an incident that killed his girlfriend, says the deadly substance was contained in a sealed box of perfume that he had found and kept at their home.

In an exclusive interview with ITV News, Rowley said his girlfriend, Dawn Sturgess, fell ill within 15 minutes of spraying the perfume on her wrists.

"I believe Dawn said she felt she had a headache and asked me if I had any headache tablets," Rowley told the British broadcaster. "I had a look around the flat, and within that time, she said she felt peculiar and needed to lie down in the bath, which at the time I thought was a bit strange."

"I went into the bathroom and found her in the bath, fully clothed, in a very ill state," Rowley added.

Rowley, 45, who said some of the liquid spilled on his hands as well, fell critically ill but eventually recovered.

Sturgess, 44, died eight days later on July 8.

The bottle of perfume was found during a search of Rowley's house in Amesbury, police have said. It was tested, and investigators confirmed the substance inside was Novichok, a deadly Soviet-designed nerve agent that was also used in a recent attack on a former Russian spy, Sergei Skripal, and his daughter, Yulia.

Rowley told ITV News that he found the sealed perfume box in a cellophane wrapper a few days before Sturgess fell ill. He had kept it at his home, before giving it to Sturgess — his partner of two years — as a present.

He told the broadcaster that he could not recall where he had originally found the box. But he was sure it was legitimate as it appeared to be unused, "which made me think it was quite safe," Rowley said.

"The fact that it was a product Dawn recognized, as a product that was quite out there and known — it's very strange," Rowley said. "It's quite scary to think that something can be disguised in that manner and left to be found in public."

Rowley, who said he feels he was to blame for Sturgess' death, said she was a "very caring, loving woman." And he offered some advice to the public:

"Be very careful of what you pick up. Whether it be cosmetics or sealed. Do not pick up anything. That's my message to the public: Do not pick up anything."

The Skripals were found unconscious on a park bench on March 4 in Salisbury, about seven miles from Amesbury.

British Prime Minister Theresa May has blamed the Russian government for the attack on the Skripals. The Kremlin has repeatedly denied any involvement.