WIBU to swap the packaging and see if MIL notices?

[fairylightsintheloft]

she has a million issues with food. One or two genuine allergies but the rest just a complete obsession with ingredients and things she thinks affect her (but don't), serious over-anxiety. Have brought a different brand of cereal that has exactly the same ingredient list as her preferred one (was in Lidl, they don't do the real one). Shall I swap the bag into the old box and see if she notices?

corous I'm the same.

Cigarettesandsmirnoff (or should that be cigarettes-and-Smirnoff-bottle-filled-up-with-lidl-own-brand-vodka?) No one is saying to bend over backwards, everyone is saying why lie?

cigarettes Not really - Most of us wouldn't bother restocking, but we certainly wouldn't resort to the underhand and frankly insulting tactics the OP is suggesting she may use

To be honest, I probably wouldn't do it anyway and certainly wouldn't be doing it to "haha tricked you" kind of thing. It was more a general wondering. She has eaten things in my house that she has later told me she doesn't like /can't have (like garlic). The q has only arisen out of the circumstances of me having this other packet. In general, for allergies, vegetarian etc I absolutely cater as needed but when its as nitpicky and frankly OTT as some of MILs are, I balk slightly. To be fair, when she stays, she usually brings stuff anyway.

In theory I'm all for it, but in practice I wouldnt do it and you probably shouldn't either.

Food fussiness does annoy me though, I understand where you're coming from.

My MIL brought her own tea cup round to mine last week FFS. I'd fantasise about doing what you're suggesting as my FIL has similar 'can't eat this' this week nonsense (decided the only alcohol he could drink was lager then decided he absolutely couldn't. DH got a crate out of it! ) but as a previous poster said, lose her trust on this & lose it forever.

op you do know you will burn in the pits of hell for even considering it!
Much hand wringing going on here!

Now if it were my mil - if I could get away with putting rat poison on her corn flakes - I would

As far as "cruelty" goes it isn't the most heinous act I can think of.

We're talking about breakfast cereal not swapping her pills for tic tacs :D

I have done this to dh before.
He will moan about instant coffee anyway if we're out of filter. But if he does drink instant he'll only drink one expensive brand. Says all the others taste like shit and will (politely) refuse coffee in people's houses and opt for tea.

I bought a Tesco's own coffee a few months back - it's about a quarter of the price of his usual. Tipped it into the coffee packaging of his usual and he happily drank it for MONTHS without noticing. So clearly a terrible brand snob and nothing to do with the flavour.

If your MIL genuinely has allergies I wouldn't. If she's just brand specific and refusing to try any others though I would.

Piano

thebody yes, I must admit that I find it hard to feign concern when the other person has, as the op describes, eaten stuff unknowingly and then later claimed to be able to consume it.

I have sympathy with food allergies/intolerances that have been diagnosed on the basis of actual observed clearly attributable ill effects, not 'I ate this once in combination with loads of other things and it was a day when I was stressed anyway so I threw up and clearly the only explanation is that it was food X', especially when they then refuse to entertain any notion of a different explanation.

I'd probably feel more inclined to play along if she tends to bring her own stuff over though, op. That is a tick in her favour - she realises it is inconvenient and tries to minimise the inconvenience to you.