How to Perform Photorejuvenation and Chemical Peeling on the Same Day
If using 20%-35% glycolic acid for chemical peeling, it is recommended to avoid visible frosting (neutralization). Ensure that the peeling reaction is mild so that both peeling and photorejuvenation can be performed on the same day, with peeling first followed by photorejuvenation.
Similarly, if salicylic acid is applied before photorejuvenation, the contact time should be shortened, avoiding obvious erythema or frosting. Other strong composite acids should also have reduced contact time to prevent significant redness or frosting.
For chemical peels with glycolic acid concentrations above 50%, or for sensitive skin with strong post-peel reactions, it is not recommended to perform both peeling and photorejuvenation on the same day, as the risk of adverse reactions increases significantly. To maximize the benefits of both peeling and photorejuvenation, it is advisable to separate the procedures into different days.
Using low-concentration acids before photorejuvenation is beneficial. If photorejuvenation is performed first, the parameters should be gentle to ensure mild skin reactions that resolve quickly (about 30 minutes) before performing chemical peeling. Personally, I do not recommend photorejuvenation followed by peeling on the same day. The preferred sequence is peeling first, then photorejuvenation.
Mechanism of Photorejuvenation (Intense Pulsed Light, IPL)
The mechanisms of IPL are based on light-tissue interactions and include:
Selective photothermolysis
Extended selective photothermolysis
Photochemical (photodynamic) effects
Photobiomodulation (light modulation)
Photoacoustic effects
For vascular lesions and hair removal, IPL primarily works via extended selective photothermolysis.
Blue light (420 nm or ACNE filter) activates endogenous porphyrins in Propionibacterium acnes, producing a photodynamic effect to treat acne.
Yellow and red light can induce photobiomodulation, provided there is no significant photothermal effect. Typical wavelengths are 590 nm, 640 nm, and 695 nm, using gentle parameters: 3 pulses, 10 J/cm², long pulse width, and long pulse delay. The endpoint is mild warmth or no heat at all, with no visible erythema.
Photoacoustic effects occur when pulse width is very narrow (e.g., 3 ms) and energy is high, producing high peak power. In single-pulse mode targeting blood vessels, the photoacoustic effect can damage vessel walls, causing purpura, which is why single pulses are not recommended.
Importance of Peak Power in IPL
Peak power = energy density / pulse width.
The strength of IPL and the risk of adverse reactions are directly related to peak power.
High peak power can rapidly heat target tissue, causing excessive thermal damage and increasing the likelihood of adverse reactions. It can also induce photoacoustic effects that damage vessels, leading to purpura. Peak power is the main factor determining IPL intensity and the likelihood of side effects.
Target Tissue for Epidermal Spots
IPL pulse width is in the millisecond (ms) range. The thermal relaxation time (TRT) of melanosomes is 250–1000 ns (average 500 ns), far shorter than the IPL pulse width. Therefore, melanosomes themselves cannot be the target for selective photothermolysis; otherwise, excessive heat would damage surrounding tissue.
Instead, the target tissue is the epidermis, which contains numerous melanocytes and melanosomes. The TRT of the epidermis is 3–10 ms, matching IPL pulse widths, allowing selective photothermal effect at the epidermal level. The target chromophore is melanin, while the target tissue is the epidermis, consistent with the extended theory of selective photothermolysis.
How Pigment is Eliminated After IPL Treatment
Millisecond IPL causes thermal coagulation of melanin (a protein). Heat spreads through the epidermis, stimulating keratinocyte differentiation. Melanosomes are carried upward with keratinocytes and eventually shed with the stratum corneum. Pigment does not enter the dermal lymphatic system unless the basement membrane is damaged.
Milestone Technological Advancement in IPL
Although “AOPT Ultra IPL” is currently popular, the 2003 upgrade to OPT (Optimized Pulse Technology) represents a milestone. Traditional IPL emitted energy in a decreasing wedge-shaped waveform; to achieve therapeutic energy in later pulses, the first pulse energy had to be increased, potentially causing skin damage.
OPT emits flat-top square pulses with uniform energy in each pulse, improving treatment safety.
