found from: The Witchipedian
The evil eye is a belief that exists in some form in most cultures. The basic idea is that if someone feels envy or jealousy and spends too long gazing a the object of their envy, their feelings can be transmitted to in the form of a bad luck curse or illness. In most cases, the envious person does not intend to harm the object of their envy but the energy of the envy takes on a life of its own.
Beautiful children, happy brides, healthy livestock and bountiful crops are especially likely to suffer the evil eye as even passersby with no other emotional connection can infect them with this negative energy causing bad luck, illness and other maledictions to befall them. If one finds oneself succumbing to envy, one can prevent the evil eye from taking hold by touching or kissing the object or person in question.
Talismans created specifically to ward off the evil eye are often created to resemble an eye or a hand and the colors red or blue is often used in their design. A red thread tied around the wrist may also be employed to ward off the curse.
Source:
https://witchipedia.com/glossary/evil-eye/
