Relief from chronic pain by low power laser irradiation.

In a double blind study, repeated irradiation with a low-power (1 mW) helium-neon laser produced relief in subjects with chronic pain. Analgesia was observed after exposure of the skin overlying the radial, medial and saphenous nerves and in some cases, irradiation of the appropriate painful nerve. Exposure of areas of skin not innervated by these nerves did not result in pain relief. Of the patients with trigeminal neuralgia, post-herpetic neuralgia, sciatica and ostearthritis, 19 of 26 experienced pain relief without the use of drugs. Patients who received sham stimulation reported no analgesia. Subjects who were exposed to laser irradiation had a large increase in the urinary excretion of 5-hydroxyindoleacetic acid, the degradation product of serotonin.