David Cameron compared his holiday jellyfish sting to dealing with Labour "invertebrates" at Prime Minister's Questions.
The Prime Minister was stung by a "very small" jellyfish while swimming in the sea during his Easter break in Lanzarote
Mr Cameron admitted he knew some of the creatures were in the water and added that his wife Samantha was "not particularly" sympathetic after the incident.
The Prime Minister was stung while swimming on a Wednesday lunchtime, when Mr Cameron would normally be facing Ed Miliband in the Commons.
He said: "I was stung by a jellyfish, it was a very small one. But as I said to my wife afterwards it was a Wednesday at the time and I'm used to dealing with slightly red invertebrates on a Wednesday lunchtime."
He told BBC Surrey: "I got a bit of a rash on my arm but it went away in about an hour. It didn't hurt very much.
"When you are swimming along and you suddenly get a bit of a sting it's a bit of a shock."
Asked if Mrs Cameron was sympathetic he said: "Not particularly, no. I've been stung by these things before.
"I love swimming in the sea and it was really nice to have some time swimming around. I knew there were some jellyfish in there so I was taking a risk which didn't really pay off."
He denied reports about his reaction to the incident , insisting: "I t didn't hurt that much, it was all right. And I didn't run out of the sea shouting 'ouch, ouch'."
Meanwhile, Mr Cameron refused to rule out sacking Grant Shapps as Tory Party chairman.
Asked by BBC Radio Three Counties whether Mr Shapps was to be replaced by Education Secretary Michael Gove in a reshuffle, the PM said: "Never believe what you read in the newspapers. Grant does a brilliant job, he's a fantastic communicator, he's a very strong colleague, he's demonstrated in his own area Welwyn Garden City how to bring people into the Conservative Party and have a mass membership party and I value his work hugely."
Asked if that meant he would not sack Mr Shapps, Mr Cameron replied: "I make these decisions at the appropriate time but I tell you Grant's doing a very good job."