Photodynamic therapy (PDT) involves the selective destruction of damaged or aged tissue using a photosensitiser that is activated upon exposure to a light source. This process induces selective cell death through the generation of free radicals following the activation of intracellular photosensitisers.
The reaction is oxygen-dependent, so PDT requires three basic elements: a photosensitiser, a light source and oxygen.
When the photosensitizer is exposed to light, its stable molecules become unstable. To return to their basal and stable state, these molecules carry out several actions, including the release of energy in the form of red fluorescence and interaction with surrounding molecules, resulting in the production of oxygen free radicals and other reactive oxygen species, causing cell death.
In addition to inducing cell death mediated by free radicals, photodynamic therapy also has indirect effects, such as the regulation of new blood vessel formation (angiogenesis), extracellular matrix formation, and immunological effects. This treatment is considered non-mutagenic, as it does not affect DNA.
The characteristics of the photosensitizer are crucial to obtaining the best results in photodynamic therapy. The most important include:
Capacity to localize specifically in damaged tissue.
Homogeneous distribution within that tissue.
Rapid time to maximum accumulation after administration.
Short half-life and rapid elimination from healthy tissue.
Activation at a wavelength with optimal tissue penetration.
High yield in the production of reactive oxygen species.
Absence of toxicity without light exposure.
Aminolevulinic acid (ALA) is the most commonly used photosensitizer in photodynamic therapy. It acts as a precursor of protoporphyrin IX (PpIX), the molecule responsible for its therapeutic effects. ALA is eliminated from the body within a period of 24–48 hours and can be administered both topically and orally.
However, ALA presents low lipophilicity, which makes its penetration into affected tissues difficult. Therefore, high doses (20% ALA) and a prolonged exposure time before light application (4–8 hours) are required to achieve optimal results.
Given these limitations, prodrugs such as methyl aminolevulinate (MAL), which is more lipophilic, and nanosomal 5-aminolevulinic acid (nano-ALA), which is more hydrophilic, have been developed. The latter has been shown to be especially effective in the treatment of actinic keratosis.
For photodynamic therapy to work, the photosensitizer needs to enter damaged or aged cells and be activated to generate the desired effect. However, the outer layer of the skin, called the stratum corneum, makes this difficult.
Fortunately, there are some pre-treatments, such as curettage, chemical peels, or microdermabrasion, that can help the photosensitizer reach deeper layers of the skin. Additionally, if the skin is already sun-damaged or inflamed, the photosensitizer is more likely to be absorbed more effectively.
In addition to these strategies, at Skin Esthetic Clinic we offer other procedures that further enhance the results of photodynamic therapy. If you are interested in this treatment, remember that we are there to help you.
Photodynamic therapy is used to treat a variety of medical conditions. Some of the most common include actinic keratosis (AK), superficial and nodular basal cell carcinoma (BCC), squamous cell carcinoma (SCC) in situ or Bowen’s disease, skin rejuvenation, acne, and alopecia, among others.
The light source used in photodynamic therapy is just as important as the photosensitizer itself. It must emit a light that is absorbed by the photosensitizer and capable of penetrating deeply into the skin. In addition, it should cause the least possible discomfort to the patient. Most treatments are performed with blue light, which is efficiently absorbed by the photosensitizer, or red light, which penetrates deeper into the tissues. Both blue or red light lamps and pulsed dye lasers are valid options. The choice depends on the condition to be treated, availability, and the professional’s experience.
In other posts from the Skin Esthetic Clinic Magazine, we have discussed the different types of light in aesthetic medicine. To better understand their use in photodynamic therapy, we can classify them into coherent and non-coherent light sources.
For PDT, various non-coherent light sources can be used, such as light-emitting diodes (LED), xenon lamps, tungsten filament halogen lamps, Waldmann lamps, fluorescent lamps, and intense pulsed light (IPL). These non-coherent light sources offer several advantages:
Handling: They are generally small and easy-to-use devices.
Coverage of large areas: They can treat large surfaces and also non-visible lesions.
High power: They reach high power levels at the desired wavelengths.
Lower cost: They are more economical compared to other options.
Safety: They are safe to handle.
However, they also have some disadvantages:
Not useful for endoscopy.
In the case of IPL, cut-off filters are required.
They can produce hyperthermia.
Blue light: Effective for treating acne, AK, and diffuse photoaging.
Intense pulsed light (IPL): With wavelengths ranging from blue to the infrared spectrum, it can excite protoporphyrin IX (PpIX) through its successive absorption bands, making it useful in photorejuvenation, acne, and AK.
Red light: Allows treatment of non-melanoma skin cancer up to a depth of 2 to 3 millimeters. It is also used to treat acne with topical ALA, although it may have significant side effects, including the possibility of basal cell carcinoma. It is the most commonly used light source with topical MAL.
Photodynamic therapy (PDT) not only reverses sun damage and prevents skin cancer, but also improves the overall appearance of the skin. This treatment can be performed with various types of lasers, such as pulsed dye lasers for blood vessels or lasers for pigmented lesions, as well as with lights that stimulate collagen production, such as red and blue light.
The goal of photodynamic rejuvenation is to improve skin quality without requiring a long recovery time. Results depend on the type of light used and may include improved pigmentation, smoother skin, and reduction of fine wrinkles. Additionally, these effects are not only long-lasting but continue to improve in the months following treatment.
Although the exact mechanism of action is not yet fully clear, it is believed that PDT acts in several ways: directly on cells, on blood vessels, and through a general inflammatory response. These effects are what produce the visible changes in the skin after photorejuvenation treatment.
The exposure time to light during treatment is not fully established. Short times (30–60 minutes) are more comfortable for the patient and have fewer side effects, but they also result in a lower concentration of PpIX, which may make the treatment less effective. Longer periods, such as 3 hours, have been observed to improve results.
To perform PDT, specific protocols adapted to each skin condition and level of aging must be followed. The most common steps according to medical literature are:
Application of the photosensitizer: MAL or ALA is applied over the entire face, with an incubation time ranging from 30 minutes to 3 hours.
Exposure to the light source: After the incubation period, the skin is exposed to the appropriate light source.
Characteristics: Telangiectasias, lentigines, and fine wrinkles.
Recommended light sources: Vascular lasers, pigment lesion lasers (Q-switch), or IPL.
Characteristics: Multiple wrinkles and laxity.
Recommended light sources: Non-ablative lasers (Erbium:glass laser), ablative lasers (CO2 laser), and semi-ablative modalities (radiofrequency).
Characteristics: Multiple actinic keratoses (AK), history of epitheliomas, and generalized aging.
Ideal candidate for photodynamic rejuvenation.
Patients with multiple AK and generalized redness: PDT with pulsed dye laser using parameters of 5 to 7 J/cm², 10 ms pulse, and 10 mm spot, seeking vascular spasm without purpura.
Patients with multiple AK, lentigines, and telangiectasias: Rejuvenation with PDT using IPL, filter 560–590 nm, 24 to 32 J/cm², and pulses of 2.4 to 4 ms.
Patients without AK, lentigines, or telangiectasias: Red light is used to improve fine wrinkles and tighten the skin.
The side effects of photodynamic therapy are generally mild and uncommon. The most frequent include redness, swelling, and skin peeling during the 3–5 days following treatment. In some cases, moderate pain during light exposure may also occur.
According to the authors’ experience, these side effects occur in less than 1% of cases and depend on several factors, such as pre-treatment steps, light exposure time, the presence of certain skin conditions, and the patient’s skin type.
To improve the effectiveness of PDT, it is important to follow certain recommendations. According to the literature, some of the most common practices are:
Remove the stratum corneum: Use techniques that remove the outermost layer of the skin, as it is the main barrier to photosensitizer penetration.
Cooling systems: Use cold air to relieve pain during treatment.
Avoid sun exposure and use sun protection: Do not expose yourself to the sun for 48 hours after the procedure.
Do not use topical anesthetics: These have a high pH that can deactivate the photosensitizer.
Treatment frequency: Perform sessions every 4 weeks with red light and every 2 weeks with blue light, depending on the protocol used. A suggested schedule includes three sessions in the first year and one annual maintenance session.
Antiviral prophylaxis: For patients with a history of herpes simplex, antiviral medication is recommended as a preventive measure.
BIOREGENERATIVE TREATMENT. An intensive repair treatment that prolongs the skin’s youthful appearance by improving its hydration and firmness.
HIGH UV PROTECTION. Intense hydration and immediate absorption. Oil-free. Can be applied to damp skin.
At Skin Esthetic Clinic, we have specific PDT protocols that allow us to offer treatments more frequently, with few adverse effects and remarkable results, such as more uniform, brighter and hydrated skin, reduction of fine wrinkles and decreased sun damage.
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PDT is a promising technique to treat photoaging in selected patients, offering satisfactory results, few side effects and a short recovery period. In addition to its aesthetic benefits, it prevents the appearance of precancerous and cancerous lesions by inducing a phototoxic reaction in non-visible lesions. Therefore, it is a cosmetic, preventive and therapeutic treatment.
Despite these benefits, more research is needed to refine current protocols. As with other aesthetic medicine treatments, better results are obtained by combining different treatment modalities.
Thanks to the ability of the photosensitizer to concentrate in the sebaceous glands, photodynamic therapy (PDT) is very effective in the treatment of acne.
PDT has several beneficial effects on acne:
Different light sources are used in PDT to treat acne, each with its own benefits:
To achieve better results, long incubation periods (3 hours) of the photosensitizer are recommended, although this may increase side effects. For this reason, shorter periods (1 hour) with multiple treatment sessions are often preferred.
The number of sessions depends on the severity of the acne. One session can significantly reduce bacteria. Two sessions are usually sufficient to see clinical improvement, with sessions every two weeks if more are needed.
It is best to start with low energy to reduce the risk of side effects such as erythema, pain, edema and reactive acne. Results can last up to 6 months.
Although PDT is safe, mild side effects may occur, such as:
PDT is a promising option for the treatment of moderate acne, both alone and in combination with other treatments. It is especially useful in recurrent cases or when other therapies cannot be used. Pulsed dye laser offers the best results for acne.
Photodynamic therapy (PDT) is an advanced and versatile technique that has proven to be effective in the treatment of various skin conditions, including skin rejuvenation and acne. Through the use of photosensitizers activated by specific light sources, PDT not only selectively destroys damaged cells, but also promotes tissue regeneration and improves the appearance of the skin. In addition, this therapy offers preventive benefits by reducing the risk of precancerous and cancerous lesions.
In summary, PDT is a promising option for both therapeutic and aesthetic purposes, with a favorable safety profile and long-lasting results. Although more research is needed to optimize protocols, this technique stands out as a comprehensive treatment that combines cosmetic and preventive effects, benefiting patients with a variety of skin conditions.
Aesthetic Medicine carried out in unauthorized centers and by personnel lacking proper training and regulated education is a serious risk to the health of our patients. At Skin Esthetic we are an Advanced Aesthetic Medicine Clinic. We perform medical-aesthetic approaches with high scientific rigor, by a duly qualified team and always focused on preserving the naturalness that only you can have. Remember, at Skin Esthetic we work so that your only concern is to think:
Why didn’t I do this sooner..?
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