In the ceremony of limpia – cleansing – the patient may sit on a wooden chair below which is a bowl of smoking copal incense. This will purify the patient’s body and is relaxing to any spirit intrusions, which are made drowsy by the smoke. As the limpia takes place, the shaman circles the patient, chanting, blowing tobacco smoke over her and stoking her body with flowers. The tobacco smoke eases the passage of the intrusion, which is then caught by and ‘re-housed’ in the flowers.

Sometimes an offerenda is also made in thanks for the healing - or to the intrusion for leaving - in which case a gift of some kind may be tied up with the flowers. The whole bundle is then taken into nature and buried so the spirit will not be disturbed and others won’t be infected by it. Coastal shamans may take the flowers to the sea instead and cast them to the waves so the tide takes them away from the shore.

In the Amazon rainforest, it is not flowers that are used, but the leaves of the chacapa bush. These are approximately nine inches long and, when dried, are tied together to make a medicine tool which is used as a rattle during ceremonies. In a healing, the chacapa is rubbed and rattled over or near the patient’s body to capture or brush out the spirit intrusion. Once he has it in his chacapa, the shaman then blows through the leaves to disperse the intrusion into the rainforest where the spirits of the plants absorb and discharge its energy.

Another way of dealing with intrusions is the use of cleansing leaf baths, a method practiced in Haiti as much as in Peru. Haitian shaman, Loulou Prince, explains:

“There are specific leaves, strong-smelling leaves, which help people who are under spiritual attack. I mix these leaves with rum and sea water to make a bath for the person, then I bathe her and I pray to the leaves to bless her. I sing songs for the spirits and the ancestors as well, and ask them to come help this person.

“The rest of the bath that is left over, I put in a green calabash bowl or a bottle, and before the person goes to sleep at night, I have her rub her arms and legs with it. When that is done, no curse can work on that person and the evil is removed”.

How this ‘evil’ comes to infect a patient in the first place has to do with jealousy.

As an example, Loulou was asked to perform a healing for a young child brought to him by a woman who had four children, two of whom had already died through the actions of spirits that came to her house at night to suck the life force from them. The woman was a market trader who had made a little money (a rare commodity in Haiti). Her neighbour was jealous and had sent spirits to kill her children.

“I bathed the child to break the bad magic. Then I gave him leaves to make his blood bitter, so it would taste and smell bad to the spirits, and they would go away. After that, the child got better; he got fat and he grew. That boy is a young man now”.

Intrusive spirits like these are believed, in Haiti, to make their home in the blood, which is why Loulou uses herbs to make the blood taste bitter and the body smell “strong”. This makes the host less appealing to the intrusion which then finds its way from the body.

‘Fire baths’ are often used in these treatments as well, where kleren becomes the base for a herbal mix which is set on fire and rubbed over the skin. The alcohol burns quickly and doesn’t hurt the patient, but it destroys the intrusion as it makes its way out of the body.

Dr Stanley Krippner, professor of psychology at Saybrook Institute, concludes from his study of traditional healing that the power of our thoughts alone - whether positive or negative - has a profound effect on our health. When we accept the psychic emanations of others, pick up on their negativity and - crucially - when we allow their negativity to be absorbed within us so we find ourselves in agreement with our enemies, we open ourselves to illness.

This, too, is the basic philosophy of sin eating. In this old Celtic tradition, a sin is viewed as a weight or ‘blemish’ on the soul which will keep it Earthbound when the sinner dies and suffering while alive. The perception of sin is a powerful force towards illness, but it is our perception that we have done wrong which creates the weakness in our souls. The shame and guilt we carry is the spirit intrusion.

The Tuvan shaman, Christina Harle-Salvennenon gives another example of spirit intrusions related to guilt: two young boys, patients of hers, who got carried away one day while they were playing and castrated a dog. When they came to their senses and realised what they had done, the boys ran home in shock. Both of them immediately became ill, one symptom of which was inflammation of their testicles.

Recognising the illness as buk, Christina demanded that the children tell her what they had done to cause its onset. The children, however, were overcome with guilt at their actions and refused to confess. Had they done so, it would have relieved the traumatic pressure in their bodies and given the shaman a direction for healing, but they simply could not. Both children died.

Spirit extraction (the removal of intrusions) was sometimes performed by the sin eater by stinging the patient’s body with nettles, paying particular attention to the ‘corners and angles’ – the backs of the knees, elbows, back of the neck and belly – where intrusions tend to congeal.

The nettle stings would heat the skin and draw the intrusion to the surface, in a similar way to the ‘fire baths’ of Haiti. It could then be washed off in a cold bath containing soothing and cooling herbs such as chamomile, lavender, rose water, and mint.

Once this was done, the patient would also be reminded of the need to make reparation to the person they had sinned against or else their guilt – and so the intrusion – might well return. One simple tradition that has survived as a way of making amends for minor sins, of course, is to send a bunch of flowers.

Sin eating philosophy, again, is in many ways consistent with the Haitian experience. Maya Deren writes, for example, that therapeutic actions may be “executed by the priest but must be carried out, in major portion, by the patient himself under guidance of the priest. The patient must himself straighten out his difficulties with the loa [spirits]… In other words, the patient treats himself, and this is another boost to his morale. Almost inevitably, no matter how ill the person is, he must take part in the rituals relating to his treatment”.