Grenz rays have been used dermatologists since the 1920's. At one time, it was an important treatment tool, but with all the recent medical advances it is rarely used today. Still, will not do the damage to the skin that is seen with prolonged use of cortisone creams. It is occasionally very helpful for conditions that fail to fully respond to other treatments. Grenz treatments are not a replacement for other treatments but are added to other treatments to get a more complete result.

Grenz rays are a form of black light. Ultraviolet light, x-rays, and gamma rays are all composed of photons, which are packets of electro-magnetic energy traveling at the speed of light. Grenz rays are photons produced at low kilovoltages giving them a very low penetration power. Half their energy is absorbed within the first half centimeter of tissue, which means that they do not penetrate beneath the skin.

Due to its very limited level of penetration, Grenz rays are classified as ultrasoft radiation. They do not carry the risks of other forms of radiation when proper radiation safety measures are followed. Grenz ray treatments should not be confused with the "Superficial radiation therapy" or "superficial X-Ray" which were used for everything from acne to eczema back 30 to 40 years ago, and are still used in the treatment of malignant skin cancers today.

The usual course of Grenz treatment consists of weekly or bi-weekly treatments over three or four sessions. Treatments giving over 200 Rads will cause a mild sunburn reaction at the site. A persistent dark, tan may linger for several months afterwards. Hair loss does not occur. Subsequent treatments may be repeated two or three times yearly, if needed. Grenz ray treatments will be reimbursed at the appropriate level by most insurers (code 77499, unlisted procedure).