Stephen-- you wrote:

I'm really talking about someone laying hands on me. I'm happy to be prayed for. Sometimes I feel that even Christian healers pass on something of their own energy. In other words, I don't know how much of the healing energy is purely sourced from the Holy Spirit.
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Derek Prince would agree with you. He writes:

Laying hands on a person in prayer is not just a picturesque religious ritual. It can be a powerful spiritual experience, a temporary interaction between two spirits through which supernatural power is released. Normally the power flows from the one laying on hands to the one on whom hands are laid, but at times it can flow the other way. The power may do either good or evil. It may emanate from the Holy Spirit or from a demon, depending on the one from whom it flows. For this reason Paul established certain safe-guards. "Do not lay hands on anyone hastily," he wrote, "nor share in other people's sins; keep yourself pure" (1 Timothy 5:22)...The laying on of hands should be done reverently and prayerfully...It is a mistake to turn a group of people loose and encourage them to lay hands indiscriminately on one another. p. 109, The Shall Expel Demons, 1998.

I think this warning applies to various forms of healing arts like acupuncture, reiki, and massage therapy, etc. as the healer's personal energy or evil spirits can easily get transmitted.