I had a salad for lunch yesterday and almost immediately
It is not related to IBS.
Hello dear, welcome to Ask a doctor service.
I read your query and here is my advice.
If this is the first time that happens to you and just for 2-3 days it is not related to IBS.
It may be a casual gastroenteritis or inflammation of intestine. This will get better in a couple of days.
You can take probiotics such enterogermina to establish the intestinal flora.
IBS is characterised by long periods of diarrhoea an constipation not related to a clearly identified cause.
Hope I have answered the question.
Let me know if I can assist you further.