Oxygen oxidizes fragrances making them weaker. Top notes tend to be the first to oxidize but the alcohol in perfume evasporates as well. Perfumes exposed to oxygen for a short period aren’t negatively impacted.
Oxygen exposure of cologne happens during the manufacturing process. It also happens slowly through evaporation. If you have a broken perfume bottle, you have a perfume that is exposed to oxygen and it will go bad in a short period.
Oxygen or air exposure of fragrances happens naturally through cologne evaporation. Volatile essential oils, aroma chemicals, and alcohols are all negatively impacted by oxygen.
The oxygenation process is often harmful to fragrances. If you remove the atomizer, you are unlikely to place it back tightly enough to prevent oxygenation and as a result, your fragrance will go bad.
What happens when the fragrance is in direct contact with oxygen?
A simple experiment shows us long periods of oxygen exposure changes cologne irremediably. Perfumes tend to darken, evaporate, and even change in scent as a result of air exposure. Most perfumes exposed to air tend to become sweeter and eventually they go off. This oxygenation process can be faster in expensive perfumes made with more natural ingredients than with aroma chemicals.
Direct oxygen contact is never a good sign for your perfume. Old salad perfume bottles sold today to show us how air changes perfumes even when the bottle is unopened. These perfumes are confused with maturation but it’s a sign of oxidation and air exposure, even if in small percentages.