When my sister got pregnant, she rang me up and asked for the small charm which my grandmother had brought from Baghdad. The charm, held together with soft bands of gold, contains two gallnuts, some turquoise discs, a tiny fish made of gold and a cowrie shell. It was unthinkable that anyone in my family could have a baby without getting protection from the evil eye.

For many Jewish people, the evil eye is not just a silly superstition, but a genuine concern. They often wear red bands, make spitting noises and mutter the words “kein ayin hara” — “no evil eye”. One ancient rabbi declared: “Ninety nine people died from the evil eye and only one from the hand of heaven”.

Fear of the evil eye has been around for at least 3,000 years and is certainly not just a Jewish concept. It spreads from China to India and Africa and through the Mediterranean up to the Arctic Circle. The evil eye is no respecter of rank. Numerous popes were thought to have the evil eye and, in the years before the Second World War, Mussolini refused to meet King Alfonso of Spain because he was reputed to have the evil eye. Whenever King Alfonso walked into a cinema, people would start jingling keys to protect themselves.

A wide variety of charms are used against the eye. The singer Madonna wears a red string. Meghan Markle has a pendant with an eye on it, Greek women carry blue beads and Italians often have key-rings with images of a hunchback. Many of the charms are frankly sexual, such as the large phalluses carved into the walls of Pompeii. In India and many Arab countries, children were intentionally not washed, so they would become less attractive to the evil eye.

The evil eye is associated with envy. Some people say the power of the evil eye runs in families. The Italian novelist Alberto Moravia considered it a force of nature — rather like gravity. In Norway it was thought a woman would get the evil eye if she suckled toads. In Eastern Europe it was believed children who were not properly weaned or who failed to pay attention in church would have this power.

In the 19th century, creative people were often accused of having the evil eye. Composers such as Offenbach and poets such as Heine were credited with causing death by the use of their evil eye.

I have spent around 20 years researching the evil eye — talking to housewives, Eritrean immigrants, Corsican jewellers and street traders in Naples. And I have acquired a strange collection of sliver charms and a library of esoteric books. It’s been an interesting journey — even if my family regards me as slightly mad.

Although my book contains a lot of serious discussion, I’ve tried to make it an enjoyable read. And it also gives useful advice. If you cannot get the milk of an Assyrian prostitute — an infallible cure for the evil eye — you can use cowrie shells or plants such as rue and rowan. If all else fails, you can dress your boys in girls’ clothing and change their names to confuse the evil eye.

Some Jewish religious groups are scathing about the evil eye and regard it as little more than a con. But a few years ago I visited the mother and baby home in Stamford Hill. There were 20 cots for newborns and in each one was a laminated prayer against the evil eye. Some people prefer to be safe than sorry.

The Evil Eye — The Magic of Envy and Destruction is available from jackshamash.com