BERLIN -- Water-filtered infrared light is an effective and painless means of removing warts, according to German dermatologists who report positive results from a small clinical trial.

Dr. Silke Fuchs from the Jena University dermatology clinic said that when infrared radiation is conducted through water, its long-wave parts are filtered out in favor of the short-wave IR-A band.

This is said to result in a reduced risk of superficial burns and a better penetration into tissues.

"This special infrared light penetrates particularly deep into the skin," she said in a statement. Heating the wart increases blood flow and stimulates an immune response to the human papillomavirus.

Fuchs and her team, led by dermatology Professor Peter Elsner, conducted a clinical study on 80 patients with warts that had resisted other treatments.

Participants were either treated with the water-filtered infrared therapy or with a "placebo" light. Of those who had the infrared treatment, more than 80% displayed a clear reduction in wart-covered area. One third of those given placebo light showed reduction.

Further treatment with 5-aminolevulinic acid (5-ALA), a chemical used in light-activated therapy, did not result in further improvement, Fuchs reported at a presentation last month at a symposium at the Braun Foundation in Luzern, Switzerland.

She reported there were no side-effects from the infrared light treatment, saying the function was to revitalize and strengthen the local immune system with the light by increasing blood flow to the wart, which is often disrupted.

Elsner said he hoped the technique would be taken up by dermatologists, and that public health insurers would add it to their lists of treatments for which they pay. "This new therapy should be suited above all for children who have been unsuccessfully treated with other methods. Admittedly at the moment the state insurers do not cover the costs. But it is to be hoped that they will take on this good-value treatment in the future."

Water-filtered infrared light is also used in some areas of oncology, most successfully with superficial tumors up to one centimeter under the skin.

Scientists at the Mainz University Institute for Physiology and Pathophysiology have reported promising results from animal experiments looking at the treatment for larger and deeper tumors, largely in conjunction with chemotherapy and radiotherapy.

"The warming effect is limited, though, as one has to reach temperatures of more than 41 degrees to get cell-kill and that is not so simple with many tumors as the blood flow tends to dissipate the heat," Dr. Debra Kelleher from the institute told Reuters Health.

Hyperthermic therapy is rarely used in the U.S., Kelleher noted, when there is some other way to deal with a tumor, such as removing it surgically.

"But in Europe use of the therapy is relatively stable," she added.

German firm Hydrosun, which manufactures the equipment used in the Jena study, states that the water-filtered infrared light therapy can be used for a wide range of other indications including chronic, degenerative joint disease; nerve inflammation and pain; back problems; scar tissue; and sinus and circulatory problems.

"The expanding use of this relatively new therapeutic modality has revealed its efficacy for the treatment of cutaneous precancer and cancers, as well as selected benign skin disorders," a company statement says.