How to understand that in front of you is an energy vampire?

Depends on what kind of meaning you mean by this concept. If on average, then an "energy vampire" can be any person, after communicating with whom you feel emotional fatigue and devastation. Moreover, it is not always a person who whines, complains and says that "everything is bad." Some people can also negatively influence the fact that they constantly demand something from you and generally fill the entire space with themselves, literally not letting you breathe. Although here, most likely, we are still dealing with hidden negativity, it is just that it is realized not by whining, but in other ways.

Only after talking to him. Some people may feel just on an intuitive level the negative of a person and the loss of their energy, being near him, without engaging in dialogue. If, in any conversation with a person, you do not feel well, at which it always happens, this is a 99% energy vampire in front of you.

It is believed that people with brown eyes are ill prone to smoothing and energy vampirism. Different sources disagree.

But each of us can be an energy vampire when: constantly complaining, whining, screaming or driving to nervous exhaustion. Any irritation of the nervous system leads to its leakage.