Red light at 675 nanometers is the most studied and promising color of light therapy for melasma. Blue light should be avoided entirely, as it triggers the skin to produce more pigment and can make melasma worse. Green and yellow light lack strong clinical evidence for melasma specifically, though they appear in some broadband devices used alongside topical treatments.
Why Red Light Targets Melasma
Red light at 675 nm has a high affinity for both melanin and collagen fibers while having minimal interaction with blood vessels. This selectivity matters because melasma involves not just excess pigment but also changes in the underlying skin structure, including increased blood vessel activity in affected areas. When 675 nm red light reaches the skin, it transfers heat to collagen fibers, causing them to shrink and triggering the production of new collagen. This remodeling effect also appears to reduce blood flow to the treated area by shrinking the collagen lining of tiny capillaries, which may help address the vascular component of melasma that other treatments miss.
Research published in Skin Research and Technology found that this wavelength also promotes types of collagen with anti-angiogenic properties, meaning they naturally inhibit the growth of new blood vessels and can even trigger the death of cells lining existing ones. This dual action on both pigment and vascularity makes 675 nm red light distinct from treatments that only target melanin on the surface.
Blue Light Makes Melasma Worse
Blue light, in the 400 to 490 nm range, actively stimulates pigment production. Skin cells contain a light-sensing protein called opsin 3 that detects blue light and sets off a chain reaction leading to melanin synthesis. This is the same reason unprotected sun exposure and screen time are concerns for people with melasma. A study examining the impact on melasma patients found that even moderate doses of blue light induced measurable increases in pigmentation, and at higher energy levels the darkening effect was comparable to what occurred in people without melasma.
If you’re shopping for an at-home LED device, check the wavelength specifications carefully. Many LED panels marketed for acne treatment use blue light in the 415 to 420 nm range. These are the opposite of what you want for melasma and could trigger a flare.
Light Therapy Works Best as Part of a Combination
The American Academy of Dermatology notes that light-based treatments can improve outcomes for melasma patients who are already using topical medication and sun protection. Light therapy alone is not considered a first-line treatment. A 2025 systematic review and meta-analysis of combination therapies (pairing light or laser treatments with topical agents like hydroquinone, azelaic acid, or tranexamic acid) found no significant benefit at four weeks, but statistically significant improvements emerged by 8, 12, and 16 weeks. This suggests the effect is cumulative and requires patience.
Interestingly, the benefit appeared to fade slightly around 22 weeks after treatment but resurged at 24 weeks, then became statistically insignificant again by 28 weeks. This pattern reflects what dermatologists already know about melasma: it’s a chronic condition that tends to recur, and maintenance treatment is part of the long game.
Common combination protocols studied in clinical trials include low-fluence laser sessions at one to three week intervals paired with daily topical lightening agents. In most studies, patients completed between 3 and 10 treatment sessions over several months. The typical recommendation is to begin a topical lightening regimen two to six weeks before starting any light-based procedure.
The Risk of Making Things Darker
The same meta-analysis found that combination therapy carried a significantly higher risk of side effects compared to topical treatment alone, with the odds roughly nine times greater. The most common adverse events were redness and post-inflammatory hyperpigmentation, which is exactly the outcome melasma patients fear most. When the skin is irritated or inflamed by a laser or light device, melanocytes can respond by producing even more pigment, leaving the treated area darker than before.
This risk is higher in darker skin tones, which also happen to be more prone to melasma in the first place. It’s the main reason the AAD emphasizes that light and laser procedures for melasma should only be performed by a board-certified dermatologist with in-depth knowledge of how different skin types respond.
What to Expect From Treatment Sessions
For professional red light treatments, protocols typically involve sessions every one to three weeks, with most studies reporting four to six sessions as a starting course. Results are not immediate. Most patients begin noticing changes in skin tone and texture after three to four weeks of consistent treatment, with meaningful improvement in pigmentation taking eight weeks or longer based on clinical trial timelines.
At-home red light devices use lower energy levels than clinical systems. If you’re using one, sessions of 10 to 20 minutes are standard, with three to five sessions per week during the initial phase. Avoid daily use for more than two to three consecutive weeks without a break, as overstimulating the skin can backfire. These consumer devices deliver far less energy than the clinical lasers used in studies, so results will be slower and more modest.
Regardless of the device, sun protection remains the single most important factor in managing melasma. Any benefit from light therapy will be undone by unprotected UV and visible light exposure, which restimulates the pigment-producing cells you’re trying to calm down.