DD is 18mo and has been diagnosed with a mild to moderate nut allergy (face, neck and chest gets red and blotchy, coughs, runny nose and sneezing) and we've bee told by hospital to avoid all nuts completely in the next 12 months. Have told both sets of dd's grandparents this and explained that although her reactions have been mild to date they could change to severe, tighten her throat, restrict her breathing and very very very worst case scenario cause death. Hence, we need to check all packaging of food to make sure no nuts.
MiL (2-3 weeks ago) had bought some co-op cookies (where you get 5-6 in a bag) and said there were no nuts. I was dubious (as I had bought similar ones from other stores and they all had nut warnings on) - she said she'd checked the ingredients so I said nothing (didn't want to overly challenge her but mentioned to DH) luckily DH said he wanted the packet, passed it to me and as I suspected there was a nut allergy warning. MiL was horrified that she could have done something so awful etc etc I said not to worry, we just need to be careful and showed her where the allergy warnings were and said even if not in the ingredients it may be produced in a factory with traces of nuts etc etc and cause cross contamination.
This weekend, DD already having a tough time as some corn flakes had kicked her reaction off. We gave her meds but she still had runny nose etc. Visiting MiL I explained alhtough she was certain DD had hayfever 
not allergic reaction. Then MiL takes DD off to the kitchen and says let me give you some cookies and starts to rummage around in the cupboard. I follow in and help to take the Cleberations box down for her... she has a a box full of odds and ends of half open packets of biscuits including some sealed Ginger Nuts and leftovers from Victorias biscuits etc. I say let's not give these to DD as other biscuits in the Celebrations box may have nuts in. Oh no, she says, pulling out a foil wrapped Victorias choccy biccy (who knows how old it was!?). I then proceed to explain, again, even if this is not a nutty biscuit it could still have traces of nuts from factory. No no no, I checked the tin, she says (tin is long gone as I suspect these biscuits have been in the box for a year plus). I leave the kitchen. She gives the biscuit to DD. DD remains runny nosed, watery eyed and sneezing for the rest of the day.
Get home - check online and lo and behold the Victorias tins do have a warning about nuts. Have written a factual email to both sets of grandparents stating why packaging needs checking (again, already told them this face to face), what the reactions are along with hospital guidance note.
I am seriously pissed off now as I don't get why she fibs about it (previously she has a history of fibbing about silly things, giving us DH / DSiL old clothes but pretending they are new - I would have taken them for sentimental value anyway. Making things and pretending she's bought them - again I think making things is a nice sentiment and no it's not because she is hard up for cash etc as she does buy things for dd too). Small fibs I don't mind but this could have caused dd harm.
AIBU??