He’s had 11 years of smelling this same dish at grandma’s so there is more to the story.
Some spice change?.............
Maybe but not necessarily.
Allergies are very unpredictable and can worsen or disappear for almost no reason.
Having allergies myself, I can believe this story. There are fragrances that set me off very easily, while others have no effect. Hit or miss and there's no telling.