Hi your mum could also be allergic to something she has eaten, as normally it can take from instantly eating to up to 4 hrs to see the symptoms, ie coughing, nose running, wheezing and many more symptoms does your mum have any more symptoms ie like aches, pains
in joints, any skin problems?
Allergies can
cause all sorts of things, my daughter 17mths as reflux which can be aggrivated or caused by allergies. I suggest she gets some allergy tests done on everything.