“Huit” is French for the number eight. “Un, deux, trois, quatre, cinq, six, sept.. achoo! Sorry, I have a huit allergy” was posted on Twitter by Joelle McNichol on February 10, 2009. “Did you hear about the Frenchman who could only count up to seven? He had a huit allergy” was posted on Twitter by FizzyDuck on May 28, 2009.
 
The joke has been credited to English comedian Milton Jones since 2013, but the joke is from at least 2009. It’s unlikely that Jones wouldn’t have been credited earlier, had he originated the joke.
   
   
Twitter
Joelle McNichol
@joellybaby
Un, deux, trois, quatre, cinq, six, sept.. achoo! Sorry, I have a huit allergy.
6:59 PM · Feb 10, 2009·Twitter Web Client
   
Twitter
❤️ FizzyDuck ❤️
@FizzyDuck
Did you hear about the Frenchman who could only count up to seven?
He had a huit allergy.
3:46 AM · May 28, 2009·Twitter Web Client
   
7 November 2009, South Wales Echo (Cardiff, Wales), “Preview” by Martin Wells, pg. 18:
Then, he’ll count to seven in French before choking biliously on the next number. “I’ve got a huit allergy,” he explains to the kind of delayed reaction he must be used to by now.
     
Google Books
Jokes for Blokes:
The Ultimate Book of Jokes not Suitable for Mixed Company
By Llewellyn Dowd and Phil McCracken
London, UK: Ebury Press
2011
Pg. 259:
Did you hear about the Frenchman who could only count to seven? He had a huit allergy.
 
22 April 2011, The Daily Mirror (London, UK), “Haye counting on ref” by Derek McGovern and John Shaw, pg. 92:
I once knew a Frenchman who couldn’t count to eight. He had a huit allergy.
     
Time Out—London
Milton Jones’s joke vault
We put the human joke factory to the test
By Ben Williams
Posted: Monday April 15 2013
(...)
France
‘I can’t even count to ten in French: un, deux, trois, quatre, cinq, six, sept… Aarrgghh! Sorry, I’ve got a huit allergy.’
   
Twitter
Crap Jokes
@TheCrapJoker
Did you hear about the French man who could only count to seven?
He had a Huit allergy.
3:30 PM · Jul 3, 2016·TweetDeck
   
Reddit—Jokes
u/Xgarthon October 16, 2016
Did you hear about the frenchman who could only count to seven?
He had a huit allergy!
 
Twitter
Shit Jokes
@ShitJokes
Did you hear about the French man who could only count to seven?
He had a Huit allergy.
4:43 PM · Dec 3, 2016·Twitter for Android
       
inews (UK)
50 of Milton Jones’s most ingenious jokes and one-liners
By Alex Nelson
Friday, 12th January 2018, 08:41 am
Updated Friday, 6th September 2019, 19:35 pm
(...)
“I can’t even count to ten in French: un, deux, trois, quatre, cinq, six, sept… Aarrgghh! Sorry, I’ve got a huit allergy.”
 
Twitter
🤣 The Dad Joke Man 😉
@DadJokeMan
I’ve never been able to count to 10 in French because of my huit allergy…                              #dadjoke
2:47 AM · Oct 1, 2018·Twitter for iPhone
 
Twitter
🤣 The Dad Joke Man 😉
@DadJokeMan
I’ve never been able to count to ten in French because of my huit allergy…
1:44 AM · Sep 19, 2019·Twitter for iPhone