What is ultraviolet (UV) light?
UV light includes the spectrum of electromagnetic radiation that is shorter than that of visible light. UV light is most commonly found in sunlight and artificial UV sources, such as tanning beds. Blacklights also produce light in the UV spectrum, with wavelengths just shorter than visible blue light. UV light is classified into 3 general groups:
UV-A (315-400 nm) – e.g. blacklights
UV-B (285-315 nm) – e.g. tanning beds
UV-C (100-285 nm) – e.g. germicidal UV light systems
Sunlight contains a full spectrum of colors, including the UV spectrum. However, shorter wavelength electromagnetic radiation is largely absorbed by the atmosphere. As a result only low levels of UV-B, and minute levels of UV-C reach the earth’s surface. UV-B and UV-C light are both capable of causing damage to DNA and the collagen matrix that supports the skin. Because of this, excessive exposure to sunlight and/or tanning booths can lead to accelerated aging of the skin and possibly skin cancer.
What does UV light exposure do?
Exposure to ultraviolet light, particularly UV-B, can cause sunburns and trigger the production of the pigment melanin in a process commonly known as “tanning”. Exposure to ultraviolet light is important for the natural production of vitamin D in the skin. Ultraviolet light can also directly damage DNA, potentially causing genetic mutations. Ultraviolet light, particularly in the shorter wavelengths, is toxic to bacteria. Longer wavelength UV light can efficiently excite the porphyrins in Propionibacterium acnes bacteria, killing the bacteria in the same fashion as blue light phototherapy.
Is UV light therapy an effective treatment for acne?
UV exposure and sunburns produce large changes in the affected skin tissue, and these changes can impact acne symptoms. Lots of people strongly believe that tanning improves their complexion. While there is certainly some truth to this, the scientific research indicates that UV exposure, tanning and sunburns are a mixed bag when it comes to acne. On the positive side, a tan (or a sunburn) can even out one’s complexion, decreasing the appearance of acne. In addition, research indicates that UV light is toxic to the bacteria that cause acne, although it is unclear whether UV light penetrates the skin deeply enough to have much benefit in this respect. It is possible that the increase in skin temperature during an acute sunburn may make sebum less viscous (less sticky), aiding in clearance of sebum plugs. Finally, UV exposure appears to modulate the immune response in the skin, inhibiting or depleting certain classes of white blood cells called Mast Cells and Langerhans Cells, which are involved in immune activation and inflammation. Depletion of these cells could potentially result in short term improvements in inflammatory acne. On the negative side, UV light can change some non-comedogenic molecules into comedogenic molecules, potentially aggravating acne in the long term. The research is indeed quite mixed on the relationship between UV exposure and acne.
How and where is UV light therapy administered?
The most common source of UV light exposure is the sun. The second most common source are the UV bulbs used for tanning. Tanning beds usually employ fluorescent bulbs that emit UV-A and UV-B light. Ultraviolet light therapy is also administered in many dermatology clinics, primarily for the treatment of psoriasis and eczema. For these treatments, a specialized source of UV-B light (310-315 nm) is commonly used.
How much does UV light therapy/tanning cost?
The cost of UV light therapy varies from free (the sun) up to ~$100 per treatment (dermatologist). The cost of a tanning session (the most common source) often ranges between $5 and $25 per session. There are no established guidelines on the amount of exposure or treatment frequency for treating acne.
References and Sources
Enhancement of comedogenic substances by ultraviolet radiation.
Mills, et al. 2006. For article abstract, click here.
Changes of comedonal cytokines and sebum secretion after UV irradiation in acne patients.
Suh, et al. For article abstract, click here.
Epidermal Langerhans Cell Depletion After Artificial Ultraviolet B Irradiation of Human Skin In Vivo: Apoptosis Versus Migration.
Kolgen, et al. 2002. For article abstract, click here.
Bivalent Effect of UV Light on Human Skin Mast Cells—Low-Level Mediator Release at Baseline but Potent Suppression Upon Mast Cell Triggering.
Guhl, et al. 2005. For article abstract, click here.
Ultraviolet phototherapy and photochemotherapy of acne vulgaris.
Mills, et al. 1978. For article abstract, click here.
Related Posts @ The Science of Acne
Additional Online Resources
Tanning Beds and Acne Discussion Board @ acne.org