There are some people who naturally have an evil eye and

three categories:

1) have it and don’t know. the evil eye can reach someone without them knowing. sunnah of mashaAllah protects both.
2) have the evil eye and know it, but they are good people. practising sunnah will protect them from harming others.
3) have it and know it and are bad people. they can use it whenever they want.

Sometimes these people are called “witches.” In reality there is no such thing, but some people have the ability described above.

Effects of evil eye

http://sunnah.com/muslim/39/56

The hadith above is very general. The way to perform ghusl is to let the person who “sent” the evil eye preform wudu’, and the water from the wudu’ be given to the victim (ma`yun) to take a shower with. This is what is referred to by the hadith above.

https://sunnah.com/bukhari/76/53

This is another treatment for the evil eye. See the page on performing ruqyah for details.

http://sunnah.com/urn/1336390

Ibn al-Qayyim said in Zaad al-Ma`ad: The evil eye is an arrow that comes from the heart of the one who has envy and the ability described above toward the one being envied and targeted. It hits the target sometimes, and missed sometimes. If when the `ayn is sent the person was exposed and unprotected (from the morning and evening adhkar) it will hit him and have an impact on him. If instead he is protected by the Qur’an and adhkar and he is someone who preserves the rituals of the deen, there is no place of entry for the arrow, and there is no impact on him.

It is possible then that the arrow returns to the one who sent it. And if Allah wills that something happen to His servant, He will cause him to forget his adhkar that day, as a test. (pg. 4/167).

Hadith: Most of ..
Silsilah 747

The effect of the evil eye upon a person can affect their possessions and things around them. This is known from experience.

The Prophet (saws)