How Does Phototherapy for Acne Really Work?

Intense pulsed light (IPL) therapy and lasers have garnered media attention as leading-edge acne treatments. Often times the effectiveness of phototherapy is credited to the destruction of a popular clear skin nemesis, the so-called "acne causing bacteria" Propionibacterium acnes (p. acnes). Yet ironically, closer examination of how phototherapy actually works paints p. acnes as a catalyst for improving acne plagued skin, not a pimple provoker.

Immonouppression stops pending pimples

In a process known as "immunosuppression" p. acnes could reduce the skin's inflammatory response to a developing an acne lesion.

Several factors like hormonal shifts, stress and nutrient deficiencies can lead to the surfacing of an acne lesion. One factor that aggravates a nascent acne lesion is the body's immunological response to all of the agents that ultimately form a zit.

One of the many cells involved in the body's immunological response to imposing acne lesions are Langerhans cells. Langerhans cells respond to foreign agents that can cause an immune response such as inflammation. Plus, Langerhans cells activate other immune cells in response to foreign attacks.

In laboratory studies, application of the common pre-phototherapy treatment aminolevulinic acid (ALA) decreased the number of Langerhans cells within the skin. This led researchers to conclude that ALA causes an immunosuppressive response in the skin.

By suppressing the actions of Langerhans cells, ALA may reduce the number of inflamed acne lesions on the skin. Other studies suggest the immunosuppressive action of aminolevulinic acid is a key acne preventative.

For instance, an investigation in the Journal of Cosmetic and Laser Therapy found that phototherapy sessions with application of aminolevulinic acid improved mild and severe acne lesions. But the phototherapy did not improve non-inflammatory acne lesions called comedones, which are pores clogged with hardened oils and dead skin cells.

Bacteria are not the acne bad guys

Medical studies have elucidated other reasons why bacteria are not necessarily acne culprits. For example, a report in the British Journal of Dermatology aimed to identify how phototherapy and aminolevulinic acid reduced a patient's acne lesion count. Ten patients with body acne took part in the study. Researchers assigned four equally acne afflicted areas of the volunteers' back to receive either an acne treatment consisting of ALA and phototherapy, ALA alone, phototherapy alone, or no treatment.

The patients received a weekly treatment for three weeks. Researchers also measured the oil secretion levels and p. acnes count of the patients before the first treatment and after the final treatment.

After three weeks of treatment, the area treated with both ALA and phototherapy exhibited a significant reduction in inflamed acne lesions. However, the oil secretion levels and p. acnes count did not drop significantly.

These findings suggest that p. acnes and oil secretion are not the root cause of acne and that phototherapy does not work exclusively by destroying p. acnes.

Acne and the sun

People have practiced do-it-yourself phototherapy for millennium using sunbathing and tanning salons. Based on available research, it's likely that when p. acnes receive light exposure, this creates a substance called porphyrin. These porphyrins can in turn reduce the presence of Langerhans cells in the skin. With less Langerhans cells circulating in the skin, an inflammatory response becomes less likely. This also reduces the chances of experiencing acne lesions.

Regardless of how phototherapy works, it looks like "acne-causing bacteria" are part of the cure, not the problem.

Sources:

Goldberg, David J & Bruce A. Russell. Combination blue (415 nm) and red (633 nm) LED phototherapy in the treatment of mild to severe acne vulgaris. Journal of Cosmetic and Laser Therapy; June 2006, vo 8, no 2 , pp 71 – 75.

Hayami, Junji; Hiroyuki Okamoto, Akira Sugihara & Takeshi Horio. Immunosuppressive effects of photodynamic therapy by topical aminolevulinic acid. The Journal of Dermatology; May 2007, vol 34, no 5, pp 320–327.

Pollock, B et al. Topical aminolaevulinic acid-photodynamic therapy for the treatment of acne vulgaris: A study of clinical efficacy and mechanism of action. British Journal of Dermatology; October 2004, vol 151, no 3, pp 616-622.