I've eaten coleslaw for quite some time and have eaten supermarket coleslaw provided it doesn't advertise itself as containing onions.
After all it is basically cabbage and carrot and both are ok so far as I'm concerned. It can be made with mayonnaise and cream. Mayonnaise is a bit iffy, as it is usually vinegar and egg. Egg is fine of course, if not better than fine. Vinegar is not - but I assume the quantities are so low it can't cause harm.
So it's better home-made with the ingredients controlled. Some commercial coleslaw contains onion, which I never eat unless its shallott. Theoretically onion should not cause too much harm because the lists all say its low in salicylate - but not entirely free of it.
About a week ago we had a meal of supermarket coleslaw and supermarket cooked chicken, which was meant to be plain chicken.
That night I had such severe indigestion I nearly dialled 111. That's the National Health Service non-emergency out of hours number. I was advised to call it by one of those questionnaires you fill in for NHS Choices, the questionnaire it flashes up if you say you have pains in your chest. Yes, you can imagine they take no chances.
Yes this was real indigestion, under the rib cage, not in the bowels, crippling pain, rising up the right side of the rib cage. No question of it being a heart attack but I'd worry about problems like stomach ulcer.
Anyway it lasted no longer than 12 hours. I went for a swim the next day and that seemed to burn it off.
Today we had the same coleslaw with our meal. It is branded as being cabbage and carrot coleslaw. I don't see why they should add onion as I would have thought it would simply make it more expensive to prepare. And, yes, now I have stomach pains coming and going, just as I write. Not as severe as last time, I hope, but the night is young.
It's not even obvious why indigestion of this kind should be caused by salicylate - except that we know that salicylate causes a reaction in whatever tissue it comes into contact with. Could that cause ulcer?
And I come back to the issue that it may not even be salicylate. A doctor friend of mine once suggested that other syndromes, specifically sulphite (sulfite), might cause similar reactions. I'm not even fully convinced that there isn't some gluten intolerance. Remember I originally thought it was a wheat allergy and abstained from wheat products for six months until tests proved it was not.
Ah well, I'm going to have to break the news I can't eat coleslaw.
* I've now checked the small print ingredients and it does contain onion together with white wine vinegar.