Blue Light Therapy: What It Is and How It Works

Blue light therapy has attracted considerable attention for its benefits against a range of skin disorders, including acne and certain types of skin cancer. Unlike ultraviolet radiation (UV light) emitted by sunlight and certain artificial sources, blue light doesn’t cause DNA damage, making it a safer, non-invasive treatment option.

As a medical writer, I have critically researched the scholarly literature on blue light therapy and will share in this article the underlying science, main therapy types, supporting evidence, and safety considerations of blue light therapy. I have also reached out to dermatology experts for an in-depth explanation of its clinical use.

What exactly is blue light therapy?

In simple terms, blue light therapy involves exposing target areas of the skin to light within the wavelength range of 415–500 nm. It delivers high inherent energy, which is believed to trigger specific biological changes. Blue light shows low skin penetration, so it is capable of acting only on the superficial layers of skin. Blue light has been demonstrated to have antimicrobial potential, which has sparked growing interest as a drug-free, non-invasive therapeutic approach.

Types of blue light therapy

The two main categories of blue light therapy are low-level laser therapy (LLLT) and photodynamic therapy (PDT). LLLT is also sometimes referred to as photobiomodulation, which is defined as a type of noninvasive therapy in which light exposure causes several changes at the cellular and tissue level via modulation of biological processes. PDT, on the other hand, is a minimally invasive therapy using photosensitive medicines that are exposed to light to kill target cells. The features of both are summarized in the table below.

How does blue light therapy work?

Photobiomodulation induces a variety of biological effects, and blue light therapy is no exception. To better understand its precise mechanism of action, I sought inputs from experts in the field.

Dr. David Johnson, a certified dermatologist based in Texas, shed some light on the events happening at the cellular level when treating acne with LLLT.

Blue light treatment (LLLT) employs a specific wavelength, around 415 nm, that penetrates through to the outermost layer of your skin. It interacts with porphyrins, which are produced by Propionibacterium acnes, the acne-causing bacteria. When exposed to this light, they will shatter and die. This clears your skin without resorting to aggressive remedies.

Dr. David Johnson

Blue light therapy works differently in the case of LLLT and PDT. To get a deeper understanding of how blue light therapy works against cancerous skin lesions, I approached a professional with hands-on experience. Dr. Geeta Yadav, a dermatologist based in Toronto, Canada, shared some insights on the PDT.

Regarding cancerous skin lesions — the treatment with PDT is done in conjunction with the use of a specialized photosensitizing medication, like aminolevulinic acid. After being applied to the area in question and exposing that area to light, a chemical reaction occurs in the treated area that deprives the area of oxygen, destroying cancer cells.

Dr. Geeta Yadav

To summarize, the effectiveness of blue light therapy in both LLLT and PDT relies on the interaction of blue light with light-absorbing compounds, which might be naturally present or externally provided. These interactions lead to photochemical reactions that cause biological changes.

What can blue light therapy help with?

Blue light therapy, used in LLLT, has been widely studied against acne. I was curious to know if there are any other skin conditions that can be improved with blue light therapy, so I encouraged Dr. Yadav to share more information.

“Studies show that blue light (LLLT) can have anti-inflammatory, anti-proliferative, and cell-modulating effects. By helping to control inflammation, it can help reduce the severity of skin conditions like acne, eczema, and psoriasis.”

Moreover, there are a few isolated reports exploring its use in atopic dermatitis, diabetic ulcers, and rosacea.

In contrast, blue light used in PDT is an intense form of light applied for actinic keratoses and some other types of superficial skin cancers. In rare cases, PDT may be used for acne treatment when other treatment options failed. Similarly, it may be used for viral skin wart treatment.

Blue light LLLT for acne

As introduced earlier, blue light used in LLLT is believed to activate endogenous chromophores, such as porphyrins, triggering the production of reactive oxygen species (ROS) that attack and destroy bacteria. LLLT can also control inflammation by reducing the secretion of cytokines such as IL-31.

LLLT is typically employed for acne treatment. A systematic review demonstrated that periodic blue light therapy (415–446 nm) for up to six weeks significantly controls inflammation and oil production, promotes the healing process, improves skin texture, and alleviates acne symptoms.

Another systematic review analyzed the data of 1,185 patients. It assessed the effects of blue and red light alone and combined. The average duration of therapy was seven weeks, administered three times a week. Following the therapy, 91% of patients reported some improvement. Only minor side effects of a temporary nature, such as irritation, dryness, or reddening, were observed.

Blue light's antimicrobial action offers a drug-free approach. It kills bacteria without affecting human cells, and the risk of developing resistance is likely to be low, which is a common concern with the majority of antibiotics.

Blue light PDT for skin cancer

In blue light PDT, the photosensitizer is selectively deposited within the tumor, generating ROS upon light exposure that destroys tumor cells. ROS also damages the blood vessels in tumor lesions, cutting the nutrient and oxygen supply to the tumor.

The FDA approved using PDT to treat actinic keratosis, i.e., precancerous lesions caused by sun damage, a couple of decades ago. PDT is also used to treat a variety of cancers and can be practiced in combination with other interventions. A recent controlled trial demonstrated that blue light PDT shows superior improvement of actinic keratosis when used in conjunction with high doses of Vitamin D3.

What to expect during and after treatment

During an LLLT session, a patient is exposed to light for several minutes without photosensitizer. The procedure is usually painless and doesn’t demand much after-care.

On the other hand, a PDT procedure is comparatively more intense and lengthy. It involves applying a photosensitizer and waiting for it to absorb, which may take a couple of hours. Then, the area is irradiated with blue light for several minutes, during which patients may experience sharp pain. Side effects include redness, peeling, and sensitivity. It is recommended to use sunscreen and moisturizer and avoid the sun for a few days.

Potential side effects and things to consider

Since PDT is administered by trained medical professionals, it is assumed that appropriate protocols are followed to minimize risks and avoid adverse effects. However, PDT is likely to have more persistent side effects, even when applied by professionals. Patients may experience redness, blisters, swelling, pain, or a burning sensation that may last from several hours to several days after the session. It is recommended that treated areas be protected from sunlight and bright light.

LLLT, on the other hand, is available to anyone through at-home devices. I was wondering if anyone could use blue light therapy, so I followed up with Dr. Johnson on the safety considerations of blue light LLLT.

Blue light treatment isn’t suitable for everyone. There are those who have photosensitivity, which is when their skin reacts poorly to light. There are also those who are using medication that makes their skin more reactive, such as antibiotics or isotretinoin. Blue light in such instances can cause burns or spots.

Dr. David Johnson

“That is why consulting with a doctor first is really necessary. I always inspect skin type, background, and medication use in my patients before I even treat them. I'm careful with three things when I use light therapy: wavelength, frequency, and dose. The wavelength varies with what we are treating,” he added.

While the short-term side effects and safety profile have been studied, limited data exist regarding the safety of long-term exposure.

Bottom line

Blue light therapy is a generally safe treatment modality for many skin diseases. It is advantageous over other treatment methods for its safety profile and quick and minimal or non-invasive nature. There are two main types of blue light therapy: LLLT and PDT. LLLT relies on light-absorbing molecules in cells to modulate biological processes, while PDT involves the application of external photosensitizers to destroy target cells. LLLT is helpful in the management of conditions such as acne and psoriasis, whereas PDT is recommended for certain superficial cancers. Blue light therapy is often accompanied by side effects. It is crucial that the therapy provider tailors the therapeutic regimen according to the disease severity, causes, and individual skin condition.