Seems there are many questions around this topics so I have updated two old posts and merged them to this one guideline to concentration types an things related. First; don’t feel stupid if you feel unsure about the abbreviations and what their purpose is. Just grab a coffee, sit down and let’s go through the basics, and soon you will see that those little letters on the bottle are not there to confuse you but rather to help you find what is right for you. If you are at home you might find it helpful to do a little exercise – go get your fragrance bottles.

Many people have a mix of perfumes, Eau de Parfum and Eau de Toilette standing in their home. (That’s another important topic: keep your fragrances in a place where they are not exposed to heat and sunlight!). It is not unlikely that this mix has been created quite subconsciously. Perhaps you preferred the EdT of one fragrance but the EdP version of another. Perhaps you just didn’t notice. Perhaps…you are confused why your fragrance does not smell like it does on your friend or like when you “tried it another time in that store…”. This post can provide you with some answers.

What do the abbreviations mean?
Perfume oil is always diluted with a solvent (ethanol or water/ethanol), so that it does not cause an allergic reaction. The abbreviations tell you the strength of a fragrance, based on the concentration of the perfume oil/aromatics used in it.

Guideline (taken from Wikipedia):
▪ Perfume: 15-40% aromatic compounds
▪ Eau de Parfum & Parfum de Toilette: 10-20% aromatic compounds
▪ Eau de Toilette: 5-15% aromatic compounds
▪ Eau de Cologne: 3-8% aromatic compounds
▪ Aftershave: 1-3% aromatic compounds

Why does it matter?
The concentration affects application, longevity and your experience of a fragrance. You don’t have to be either a perfume, EdP- or an EdT-person. Stay open to experimenting and finding your personal comfort level from fragrance to fragrance. Think about situations. Ask yourself how impactful you want your scent to be, to others and to yourself. However, it is also not unusual that someone does in fact prefer one of the categories. For example, I am a perfume person, probably to a large extent because I am drawn to base notes. 

Quick summary
Perfume: gives you the fullest, purest, most long-lasting experience of the fragrance. Perfume is gently caressed onto skin, not sprayed.
Eau de Parfum:
 has lower concentration than perfume and is often focused on heart notes. Still provides you with a rich sensation.
Eau de Toilette: 
the concentration of perfume oils is not so high and if you want the scent to last the entire day you will probably need to reapply it. It is the lightest version of a fragrance.

Application: pulse points or mist
Traditionally, experts recommend putting your fragrance on your pulse points, that is on the wrists, behind your ears, on neck, behind the elbow and backs of your knees. If you do all of them or just one is highly individual. I have a couple of perfumes that I avoid having near the face but love on the wrists for example. Also the sillage affects what application amount/method works best. A perfume that diffuses a lot should be applied with caution. Perfume is gently applied to pulse points and don’t rub it when it is on the skin.

A more modern method is that of spraying your fragrance in the air and then stepping through the mist. This works great for an EdP or EdT. Nota bene, spraying here means once or twice, not more. You might also have read about perfume in your hair – applied by spraying your fragrance on your brush before brushing your hair. 
Key message: be moderate. Too much perfume is never a good way to go. Never.
Photo Frank Carter 
It should be added here that fragrances do last longer or shorter, not only depending on perfume oil percentage, depending on the person. For example if you have dry skin you are likely to feel like your fragrance evaporates faster.

You know already that fragrances smell differently on different people. But a fragrance can also seem different on you from one occasion to another. Stress, medication or hormonal changes can make a fragrance smell in a new way, (probably worse, if you noticed it). That also explains why sometimes people use their old favorite fragrance and suddenly do not like it at all. Try another one, or just give it some time and then re-unite.