A couple of observations..
I used too work in catering, it is nearly always very hot within a kitchen environment even in winter, sometimes 40c+, towards the end of working i noticed my body tolerated the heat of the kitchen less and i would sweat more, by the end of the session i would be rinsed in sweat which isn't nice or exactly healthy or in regards too food hygiene.
Around the same time..
I also used too cook for my grandfather a couple of times a year whilst my parents went away on holiday, it was a food holiday for my grandfather in his 90's, he loves a curry,stir fry or spag bol, I would cook and grandfather would have his feet up till it was ready, as i dished up i heard my grandfather say "that smells loverly", he was in another room, myself cooking it or me sat above the plate could smell nothing.
Perhaps it is the pores in our skin that have changed in someway including the senses within our nostrils altering the way we smell physically via the proteins and oils in the pores of the skin, producing an odour and the way we sense smell and taste through our tongues.
Before awareness & diagnosis we already know for example what beef or an orange tastes or smells like so essentially that isn't totally lost if we no longer recognise it.