The difference would be that when the gut is leaky, foodparticles may enter the bloodstream through the inflamed gut lining and cause reactions within a minute.
Those who react to the smell of it are usually, biblically, allergic to it.
If leaky gut autoimmunities cause allergic reactions through smell only, is not propable, but even if such situations occur it might be a chemical reaction for example evaporated alcohols (benzyl/propyl/methyl), sulphate or phosphor, who knows really so at an narrow angle it can hose an open question.