Laser, IPL, and Light-Based Therapies
Physics in one sentence
Selective photothermolysis means matching a wavelength to a chromophore - melanin, hemoglobin, or water - and delivering that energy in a pulse shorter than the target's thermal relaxation time, so the target heats while surrounding tissue is spared. Fluence is energy per area; spot size and pulse duration change how deep and how selectively energy lands. Longer wavelengths penetrate deeper, which is why 1064 nm neodymium-doped yttrium aluminum garnet is safer for deeper Fitzpatrick types than 755 nm alexandrite.
Laser versus IPL
IPL is intense pulsed light: broadband, non-coherent, filtered light, not a laser. It is effective for pigment, vascular concerns, and hair reduction, but it is less selective and more dependent on operator skill. Know your device's wavelengths, filters, cooling method, and cleared indications, and never exceed manufacturer parameters.
Safety essentials
Eye protection for client and operator, matched to the wavelength - opaque goggles, not sunglasses. Perform and document a test spot, usually read at 24 hours. Confirm no recent sun exposure or tan, no photosensitizing medications such as tetracyclines, isotretinoin, or St. John's wort, no pregnancy, no active infection, and no history of keloids or seizures for IPL.
Adverse events
Burns, blistering, hypo- or hyperpigmentation, and paradoxical hypertrichosis all occur. Stop, cool, document, refer, and file an incident report. Never promise permanent hair removal.
Traps: calling IPL a laser; treating a tanned client; assuming one setting suits all skin types; using clear eyewear because it looks protective. Rule of thumb: if the skin is tanned, reschedule - two to four weeks of no UV exposure before treatment.