Observing self-hygiene is one rule of life but there are some people who cast caution to the wind when it comes to keeping themselves clean.
Maintaining self-hygiene requires that you pay attention to every little detail and body part on your body to always stay fresh.
However, it is common that those who do not observe personal hygiene never take notice of the strong bouts of unpleasant body odour coming from their bodies.
The reason, according to the Washington Post, is simply that the foreign smell molecules from the body repeatedly bombard smell receptors in the nose. If this goes on for a longer period of time, the receptors are overrun and tend to tire out.
As such, you will not have the sense to exquisitely smell that particular odour on your body.
If this goes on for a longer period of time, the body will acknowledge the smell and it will be registered in the brain as 'familiar.'
At that point, the stronger it gets, more information from it is embedded in the brain and it becomes a normal thing.
Once it is permanently a part of you, you will not be the one to notice; it will be other people you interact with who will notice this change.
In real life, if you are so much used to using a certain brand of a perfume, it gets to a point you don't feel the perfume's fragrance because it is already registered in your brain.