Almost a tie with " Get Smart ": Kiss of Death, Airdate: Saturday, Dec. 31, 1966 , 8:30 PM, Writers: Stan Burns and Mike Marmer, Director: Bruce Bilson Max rescues Tracy Dunhill, a rich heiress who then falls in love with him.
Unknown to Max, Dunhill is actually a member of the Daughters of KAOS.
She is seeking revenge against Max, who killed her father, the founder of U.S. KAOS.
She invites Max to a party at her apartment where she will kill him with poison lipstick .
Agent 13 is stationed inside a sofa in the apartment, but he's drunk and unable to save Max from the deadly lips.
As Richard pointed out, there's also this autobiographical reference:
From an interview with Baroness Carla Jenssen in The Brownsville Herald, by Gilbert Swan, May 31 1932: Despite the girlishly engaging gesture, the reporter shuddered just a little.
"Just a few years ago," he suggested, "had I but smelled this bud
—there would have been sudden sleep—I would have awakened hours later from drugged dreams—"Yes, that's quite true!"
came the calm reply. "
And if you had accepted one of my cigarettes something similar might have happened.
Had you wooed me, and been a man who held secrets of state or information I wanted—well, you might have fallen in love with me.
At least, I should have pretended to be a seductress.
And when a man kissed me—again, morphia!
For coated on my lips, on my teeth and on the roof of the mouth was a certain lethal preparation.
We who were in the service and were women were trained to apply it, with a thin coating to protect ourselves.
When men kissed, the coating came off—and then I would search their rooms, their baggage and their clothes until I found what I wanted."
...
...
She is the Baroness Carla Jenssen, late of the British secret service.
Now she has arrived in America but recently from London to discuss arrangements for a prosaic lecture tour, to look over the American radio broadcast prospects and check up on the filming of a book, "I Spy," which she wrote concerning her adventures.
Jenssens's " I Spy " was published in 1930, by Dodd, Mead & company and by Jarrolds.
It doesn't look like it has been... scanned?
ebooked?...
It looks like it's not commercially available in a downloadable format yet.
scifi.stackexchange.com/users/26367/Joe L.
No idea who invented the concept, but the first time I read about it in a Sci Fi Novel as a teenager was in the Mag Force 7 series from Margaret Weis and Don Perrin.
I think it was Knights of the Black Earth (but it might have been Robot Blues), published in 1995 (96 for Robot blues), so before the Firefly series.
Raoul de Beausoleil has perfectly applied lipstick during a ball.
I'm almost certain
he mentions he has a cover layer to prevent it touching his lips and he admits after the assassination is complete he'll take the antidote just to be sure.
He leaves a perfect kiss mark on the back of the hand of his mark who jokes to his friends about it.
(It mentions his lipstick assassination in this Wiki article)
http://en.wikipedia.org/wiki/Star_of_the_Guardians
I'm sure someone can come up with an earlier example, but that's the first time I encountered it.
scifi.stackexchange.com/users/24882/Mikey Mouse
The earliest reference to it can be found in North by northwest (1959).
Mr. Tornhill (played by Cary Grant) goes to the art auction where he meets the villain.
Until then, the villain had been trying to kill him by various methods.
He had hired a woman to play muse to Cary on a train which Cary comes to know after the assassination attempts on him.
Cary, in his characteristic style confronts him with the question:
"I wonder what subtle form of manslaughter is next on the program.
Am I to be dropped into a vat of molten steel and become part of a new skyscraper, or are you going to ask this female to kiss me again and poison me to death?"
scifi.stackexchange.com/users/97070/Hemant Shinde
Possibly still not the inventor, and it was fantasy, but poisoned lipstick showed up in the November 21, 1966 episode of Gilligan's Island , "The Invasion", as part of Gilligan's dream of being a super-spy.
Although, looking at some descriptions of the episode, it fails at the "doesn't harm the wearer" test, although apparently because Gilligan's kiss (wearing plastic lip protectors) is so vigorous that the poison "bounces back" on her.
scifi.stackexchange.com/users/23243/FuzzyBoots
Another early reference of poisonous lipstick includes a fictional super-villain in the DC comics and movies, Posion Ivy , particularly during her first appearance in book #181 of a Batman comic series in June 1966 .
Because of this, she is commonly in association with the superhero Batman, but one of her special abilities is having poisonous lipstick.
Poison Ivy was created by Robert Kanigher and Sheldon Moldoff, where she used plant toxins and mind-controlling chemicals to defeat her enemies, in addition to the poisonous lipstick.
An example of her using her poisonous lipstick is in the movie, Batman & Robin , made in 12 June, 1997 .
An example of her using her mind-controlling special ability is in a 2009 comic book Batman HUSH written by Jeph Loeb and pencilled by Jim Lee, where she takes control of Superman in the last part of Chapter Four: The City, but that is irrelevant to the topic of the question (although it nonetheless provides some insight into her character).
This may not be a full answer, because the ticked answer above has perhaps the earliest reference, but I wanted to add to that answer.
I am also new to all of this.
scifi.stackexchange.com/users/97071/Mr Pie
In the Firefly episode “ Our Mrs. Reynolds ”, Saffron is able to temporarily knock out Mal by getting him to kiss her after treating her lips with some kind of knock-out agent (Inara later gets some of the same).  In Doctor Who, Professor River Song uses a similar technique – an  hallucinogenic lipstick  to escape her cell when she needs to.  My question is – What is the earliest reference in a work of science fiction/fantasy to a lipstick that would  poison the kissee but not the kisser?
What is the earliest reference to a poisoned lipstick in a work of science fiction?
scifi.stackexchange.com
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scifi.stackexchange.com/questions/66681
scifi.stackexchange.com/users/3745/Affable Geek
The earliest reference of a poisoned lipstick may be Jenssens's " I Spy ", published in 1930. The earliest reference to a poisonous lipstick that would poison the kiseee and not the kisser may appear in: North by Northwest (1959); Knights of the Black Earth (1995); Robot Blues (1996); Gillian’s Island episode "The Invasion" (1966); Batman Comic Series (1966); Mag Force 7; I Spy (1930); or "Get Smart" Kiss of Death (1966)
The earliest reference to a poisonous lipstick that would poison the kiseee and not the kisser may appear in: North by Northwest (1959); Knights of the Black Earth (1995); Robot Blues (1996); Gillian’s Island episode "The Invasion" (1966); Batman Comic Series (1966); Mag Force 7; I Spy (1930); or "Get Smart" Kiss of Death (1966)