The vile musk which Gloom are infamous for is not the only scent the grass/poison pokemon is capable of producing. Much in the same way it can choose to spray sleep powder or stun spore, a Gloom can also activate various scents, most notably a sweet one like a Hoppip's which draws pokemon near.
The way this scent is used varies from Gloom to Gloom, and some say depends more on the trainer than the pokemon. Some Gloom, if their trainer endures their smell and treats them with kindness, will release this sweet scent in their trainer's presence. Other, more mean-spirited or mistreated ones will use it to draw people close, than switch odors to its noxious smell and release fumes which often require hospitalization of all those who inhale them.
Interestingly, while the noxious smell is distilled into a perfume, the sweet one is more commonly used by athletes as a deodorant. After a few hours when bottled, all that remains of the sweet fumes are its abilities to block other smells and attract wild pokemon.
