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Blue Light /Photodynamic Therapy For Acne

Other than the treatment of skin cancer, the uses of photodynamic therapy also include the treatment of cutaneous lesions of Bowen’s disease, psoriasis, and cutaneous T-cell lymphoma. It has also gained much importance lately among the various treatments for acne currently available and is generally known as blue light therapy for acne.

Though photodynamic therapy has been employed in photorejuvenation and as a treatment for acne only recently have the results shown significant potential. The advantages of photodynamic treatments for acne include the capacity for noninvasive targeted therapy via topical application of the drug and local irradiation limited to a small area of acne. These acne blue light treatmentshave showngood ability to generate excellent cosmetic results with minimal discomfort.

The inclusion of photodynamic therapy (PDT) in the range of light based acne treatments available for acne is the most recent advance in acne therapy. Not all the skin care treatment clinics are making use of this new and revolutionary technique which was previously only used as a skin cancer treatment. However, research shows excellent results with the blue light photodynamic therapy for acne have been obtained both intreating men and women in different body areas.

The photo dynamic Blue Light acne treatment involves three mechanisms of action against acne. The treatment inactivates the bacteria that trigger acne, exfoliates the skin to unclog pores, and the most exciting part of the therapy is that it shuts down the sebaceous glands in the skin. This is exciting because sebaceous glands are the root cause in the formation of acne so it has a long lasting effect even on severe acne.

Origin of Therapy

The use of sunlight for the treatment of various skin disorders (heliotherapy) was known to ancient Indians and Greeks. In the modern era, Oscar Raab, a German medical student first reported the death of Paramecium caudatum (a protozoan) after light exposure in the presence of acridine orange in the year 1900. His professor, von Tappeiner, coined the term "photodynamic" to describe oxygen-consuming chemical reactions in vivo (in the body). Von Tappeiner and Jesionek (a dermatologist), in 1904, used topical eosin and visible light to treat skin tumors. Researchers experimenting with self-injection of porphyrins noted sunburn due to PDT reactions in their skin.

Principle of Photo-dynamic/blue light therapy for acne

Photodynamic therapy combines the energy of light and the action of light sensitive agents (such as porphyrins) in an oxygen-rich environment to destroy the pathogenic cells.

As a treatment modality the therapy involves the administration of a photosensitizing compound, accumulation of the sensitizer molecules in the target cells followed by selective irradiation of the lesion with visible light (blue light) or laser light. The drug and light are individually non-toxic, but in combination they destroy tissues.

After systemic administration, photosensitizing compounds are taken up by most normal and malignant cells, but are retained longer in tumor cells and very active cells like those in sebaceous glands. The photosensitizers which are commonly used for the therapy are porphyrins which are a component of hemoglobin pigment, which in turn is a component of red blood cells. Hemoglobin is what carries oxygen in the blood.

Porphyrins have enough capacity to absorb energy from photons (particles of light) and transfer this energy to surrounding oxygen molecules. The result of this reaction is the generation of lethal oxygen species such as singlet oxygen and free radicals. These chemical species are very reactive and can damage proteins, lipids, nucleic acids and other cellular components. Porphyrins utilize energy from light to produce toxic oxygen species and this helps to destroy the cells in their immediate vicinity.

There are two types of porphyries, Hematoporphyrin derivative (HPD) and porfimer sodium (Photofrin®)which are commonly used in the systemic therapy - both are derived from animal hemoglobin.

Source of Light for Photo activation

The therapeutic window for PDT is between 600 nm and 1200 nm as light of wavelength below 600 nm is absorbed by hemoglobin in the tissues and that above 1200 nm is absorbed by water. Light sources may be coherent (lasers) or incoherent.

When porphyrin photosensitisers are used, lasers of a wavelength around 630 nm are required to match their absorption maxima. Argon pumped dye lasers (630 nm) or gold vapor lasers (628 nm) are traditionally used but they are expensive and need regular maintenance.

Nd-YAG lasers (690-1100 nm) are used for non-porphyrin photosensitisers and are very convenient to use.

Incoherent sources of light used were previously the equivalent of slide projectors with or without red light filters. More recently, Light Emitting Diodes (LEDs) and florescent light sources are being used as alternative light sources for large surface areas. These incoherent light sources are more convenient than lasers but they need longer treatment times.

A typical PDT session

  • Intravenous injection (I.V.) or topical application of a photosynthesizing agent such as a porphyrin. Usually in the treatment of acne, the photosensitizing agent is just applied topically to the skin
  • Permit time for systemic porphyrins (I.V. injection) to be cleared from normal tissues and be preferentially retained by rapidly growing tissues (e.g., cancer or psoriasis), or for topical porphyrins to be absorbed by the skin.
  • Application of light to provide the catalyst for chemical reactions.
  • Generation of toxic oxygen species in illuminated tissues.
  • Tissue damage occurs.

Side effects and their management

  1. Burning pain, stinging or itching in the illuminated area is generally experienced during light exposure which subsides after few hours of the treatment.Local anesthesia or premedication with benzodiazepine may help control the pain.
  2. Erythema and edema of the treated area may occur after light exposure and may be treated by mild topical corticosteroids. A light overdose may lead to blistering, ulceration and excessive necrosis for which a higher dose of corticosteroids may be required.
  3. Crusting and scaling accompanied by pruritus which heals anywhere between 2 to 8 weeks. Urea-containing ointments help resolve dry crusts and accelerate re-epithelialization.
  4. Systemic photosensitisers can cause long-lasting generalized cutaneous photosensitivity and phototoxicity manifesting as burning, stinging, erythema, edema and bullae formation. Sunlight, bright spotlights, photocopy machines, photographic flashlights, medical examination lights and operation lamps are all to be avoided. Ordinary indoor light is usually safe and may help in photo-inactivation of residual drug molecules in the skin.
  5. Photophobia and ocular discomfort.
  6. Residual hyper and hypopigmentation.
  7. Systemically administered photosensitizing drugs may cause vomiting, nausea, a metallic taste, and liver toxicity and are especially hazardous for patients with porphyria.
  8. Reactivation of psoriasis and malignant melanoma has been reported in some cases.
However, the merits of PDT far outweigh its negatives in most cases, and there is no doubt this modality popularly known as blue light therapy for acne and for skin cancer treatment is going to be an important part of the dermatologists' armamentarium in the future.

Though more clinical, biochemical and physical research is surely needed to support the blue light therapy for acne, there is no doubt that PDT is becoming an increasingly popular treatment approach in treatments of acne.


   
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