What Is Phototherapy? A Clear, Science-Based Guide

What Is Phototherapy? (Quick Answer)

What is Phototherapy? Phototherapy uses specific wavelengths of light to influence how cells and tissues function. It is not general light exposure. Instead, it relies on targeted wavelengths for specific purposes, from UV-based medical treatments for conditions like psoriasis to LED-based red and blue light used for skin and recovery. Depending on the wavelength, it may be used in clinical settings or at home.

What Phototherapy Actually Refers To

Phototherapy uses specific wavelengths of light to influence how cells and tissues respond. Different wavelengths are used for different purposes. Some are used for inflammatory skin conditions, others for acne, and others in settings where tissue repair is being studied.

It is not the same as regular sun exposure. Phototherapy is controlled. The wavelength, intensity, and exposure time are set depending on the goal. In clinical use, it is most often associated with ultraviolet light for conditions like psoriasis, eczema, and vitiligo. At-home devices are usually non-UV, using red or blue light for acne or general skin-related use.

The idea itself is not new. Niels Finsen received the Nobel Prize in 1903 for treating skin disease with light. What has changed is how targeted these treatments are now. Today, phototherapy includes both medical UV protocols and LED-based approaches such as photobiomodulation.

For more detail on how light interacts with cells, see our article on photobiomodulation therapy.

Is Phototherapy the Same as Light Therapy?

Usually, yes. In everyday use, people use “phototherapy” and “light therapy” to mean the same thing.

The difference shows up more in how the terms are used. Phototherapy is the more precise term and is common in medical or research settings, where it refers to specific wavelengths used for a defined purpose. Light therapy is broader. It can include medical treatments, but also things like light boxes for mood or general at-home devices.

Is Red Light Therapy a Type of Phototherapy?

Yes. Red light therapy sits under phototherapy.

It uses red wavelengths, usually around 630 to 660 nanometers. Sometimes near-infrared is included when deeper tissue is involved. Most of the research around it looks at energy production in cells, inflammation, and repair.

It is just one part of the category. Phototherapy also includes UV treatments used in dermatology, blue light for acne, and bright light used for sleep and mood.

How Does Phototherapy Work?

Phototherapy works by using specific wavelengths of light to interact with cells and tissues in the body. These wavelengths are measured in nanometers, and they determine how deeply the light penetrates. In general, shorter wavelengths act closer to the surface, while longer wavelengths can reach deeper layers.

After that, the differences become more practical. UV light is used in dermatology because it acts at the skin level and can affect immune activity in conditions like psoriasis. Red and near-infrared light are used in a different context. They are studied more for their role in inflammation, cellular activity, and recovery.

You will often see the term photobiomodulation used here. It usually refers to LED-based treatments where the goal is to influence how cells function, not to remove or damage tissue.

This is also where people mix it up with lasers. Both use light, but they are not doing the same thing. Lasers are concentrated and used for cutting or resurfacing. Phototherapy is lower intensity and works more gradually.

What Happens in Cells During Phototherapy

Cells do not respond to all light the same way. Certain molecules, known as chromophores, absorb specific wavelengths. That interaction is what drives most of the biological effects seen in phototherapy.

In red and near-infrared applications, attention is often placed on cytochrome c oxidase, an enzyme linked to mitochondrial activity. It is studied in relation to how cells manage energy and signaling, particularly in the context of ATP production.

In simpler terms, this has been linked to:

• changes in how cells use energy
• support for repair processes
• shifts in inflammatory signaling
• local circulation changes in some cases

Not all of these pathways are fully mapped. Some mechanisms are supported by consistent findings, others are still being explored.

UV phototherapy does not follow the same pattern. It is used in dermatology to slow rapid skin-cell turnover and adjust immune activity in the skin. That difference is part of why it is effective for conditions like psoriasis, and also why cumulative exposure needs to be managed.

Why Wavelength Matters: Not All Light Works the Same

Light does not behave the same across the spectrum. The wavelength changes both how far it travels and what it tends to affect.

You can see it in how different types are used:

• Blue light (415–450 nm) stays close to the surface. Most often it comes up in acne, where it interacts with compounds inside acne-related bacteria.
• Red light (630–660 nm) reaches further into the skin. It is usually discussed in relation to inflammation and general skin-related processes.
• Near-infrared light (810–850 nm) goes deeper than visible light. This is where it starts to show up in muscle and joint contexts.
• UV light is different again. It works at the skin level and is used clinically to manage immune-driven skin conditions like psoriasis.

So even though it is all “light,” the effects are not interchangeable. Changing the wavelength changes what the treatment is actually doing.

The Different Types of Phototherapy (and How They’re Used)

Phototherapy includes several distinct modalities, each defined by the wavelength it uses and the biological target it is intended to influence.

Looking at these side by side, the differences become more obvious. Some are used in dermatology, others show up in recovery or circadian-related use.

UV Phototherapy (UVA, UVB, Narrowband UVB)

UV phototherapy is what most people think of as medical light treatment. It uses ultraviolet light in a few forms:

• UVA (320–400 nm)
• UVB (280–320 nm)
• Narrowband UVB (311–313 nm)

You usually see it in dermatology clinics for psoriasis, eczema, or vitiligo. Narrowband UVB comes up the most. It is used to slow down skin-cell turnover and help settle inflammation in the skin.

It works, but it is handled carefully. Sessions are spaced out and adjusted along the way.

Red light therapy gets grouped into the same conversation sometimes. It is not the same thing. Our guide to red light therapy for psoriasis goes into where it fits, but it is a different approach from clinic-based UV.

Red Light Therapy (630–660 nm)

Red light therapy sits on the non-UV side of phototherapy. It usually uses wavelengths in the 630 to 660 nm range.

This is the part of light therapy that tends to come up around skin and recovery. You’ll see it discussed in terms of inflammation, healing, and general tissue support, often under the broader idea of photobiomodulation.

Most of the devices people use at home fall into this category, usually LED-based. You will also see it in some clinical settings, but not in the same way UV phototherapy is used.

For a closer look, see our guide to red light therapy for skin.

Blue Light Therapy (415–450 nm)

Blue light therapy stays close to the surface of the skin and usually comes up in acne treatment.

Its role is tied to compounds produced by acne-related bacteria. These react to blue wavelengths, which is why this type of light is used in that context.

You will see it used in clinics and in at-home devices, often alongside red light rather than on its own.

For more detail, see our guide to LED phototherapy for acne.

Near-Infrared Therapy (810–850 nm)

Near-infrared (NIR) sits just beyond visible red light, usually in the 810 to 850 nm range.

It is used in a different context than surface-level treatments. This is where it starts to come up more around muscle, joints, and deeper tissue.

You will usually see it grouped with red light under photobiomodulation, though it is doing something slightly different in terms of depth.

Most devices combine the two rather than separating them. Red light for the surface, near-infrared for deeper layers.

Bright Light Therapy

Bright light therapy is used more for circadian rhythm and mood than for skin. It usually involves sitting near a bright light source, often a light box, at set times of day.

You will mostly see it in the context of Seasonal Affective Disorder and sleep-wake issues. It works by shifting the body’s internal clock rather than acting on the skin or deeper tissue.

It sits in the same broad category as other types of phototherapy, but the use case is very different.

Full-Spectrum and Combination Devices

Some devices combine more than one wavelength, usually blue, red, and near-infrared, in the same unit.

You’ll often see them described like this:

• blue light for surface-level acne
• red light for skin and inflammation
• near-infrared for deeper tissue

In practice, the idea is to cover different layers at once rather than focusing on a single target.

Not all devices are built the same, though. Output, wavelength accuracy, and consistency can vary quite a bit, and that tends to matter more than how many colors are included.

Where Phototherapy Is Actually Used

Phototherapy shows up in a few different areas, depending on the type of light.

In dermatology, it is used for conditions like psoriasis, eczema, vitiligo, and acne. UV-based treatments are usually handled in clinical settings. Red and near-infrared light come up more in skin-related use, recovery, and inflammation. Blue light is mostly tied to acne. Bright light therapy sits in a different category, used for sleep and mood.

There is also a growing list of areas being studied:

• wound healing
• collagen and skin texture
• hyperpigmentation
• joint and muscle recovery
• hair growth
• neurological and cognitive use

Some of these are already part of standard care, while others are still being explored.

Clinical vs. At-Home Phototherapy: What Actually Changes

The main difference between clinical and at-home phototherapy is not just location. It is also the type of light, the dosing precision, the treatment goal, and the level of supervision.

Clinical phototherapy usually involves UV-based protocols delivered in dermatology clinics or hospitals. These treatments are used for diagnosed medical conditions and require careful dose control because UV exposure is cumulative.

At-home phototherapy more often refers to LED-based devices that use red, blue, or near-infrared light. These products are used for goals such as acne support, skin appearance, or general recovery. They offer convenience, but device quality and treatment consistency vary widely.

At-home LED phototherapy should not be presented as a substitute for dermatologist-supervised treatment for a diagnosed skin condition.

What the Research Actually Shows So Far

Phototherapy’s effectiveness varies by modality, with some applications well established in clinical practice and others supported by a growing but still evolving evidence base.

Where the Evidence Is Already Strong

The strongest evidence for phototherapy comes from UV-based dermatology treatments and selected acne protocols.

Narrowband UVB for psoriasis is one of the most established forms of phototherapy and has been used for decades in clinical practice. In dermatology, it is considered a standard option for conditions such as psoriasis because it can help regulate abnormal immune activity in the skin and slow excessive skin-cell turnover.

Blue light therapy for acne also has a meaningful evidence base, particularly for mild to moderate inflammatory acne. Its mechanism is relatively well understood: blue wavelengths interact with porphyrins produced by acne-related bacteria, helping reduce bacterial activity at the skin’s surface.

These are among the best-supported applications of phototherapy, although treatment outcomes still depend on protocol design, dosing, and patient selection.

Where Evidence Is Still Building for Red and Near-Infrared Light

Red and near-infrared light therapy have a growing body of research behind them, particularly in areas related to skin health, inflammation, and tissue repair.

Studies suggest these wavelengths may:

• support mitochondrial activity and ATP production
• influence inflammatory signaling pathways
• assist recovery-related processes in skin and soft tissue

However, results vary widely depending on device type, wavelength, intensity, and treatment duration. Compared with UV phototherapy, the evidence base is less standardized.

Where the Science Is Still Developing

Phototherapy continues to be an active area of research.

Emerging areas include:

• hair and scalp health
• neurological and cognitive applications
• long-term at-home device use
• standardized dosing and treatment protocols

One of the main challenges in this field is inconsistency. Studies often use different devices and treatment parameters, making results difficult to compare across research settings.

Clinical vs. Preclinical Research: Why the Difference Matters

Phototherapy research gets discussed at different levels, and not all of it means the same thing in practice. It helps to distinguish between preclinical and clinical evidence.

• Preclinical research includes laboratory and animal studies that explore biological mechanisms
• Clinical research involves human trials and provides more direct insight into real-world outcomes

Both are important, but they serve different purposes. Mechanistic findings do not always translate directly into consistent clinical results.

How Safe Is Phototherapy?

Phototherapy safety depends heavily on the type of light being used.

UV vs. Non-UV Phototherapy

This is the most important safety distinction.

UV phototherapy is medically valuable, but it involves cumulative ultraviolet exposure. That means it must be delivered under professional supervision, with careful dose tracking and monitoring.

Red, blue, and near-infrared LED phototherapy do not use UV radiation and generally have a lower-risk safety profile when used as directed. These modalities are non-ionizing and do not work through the same mechanism as UV.

Common Side Effects to Be Aware Of

Even lower-risk forms of phototherapy can cause mild side effects in some users, including:

• temporary redness
• warmth
• dryness
• sensitivity in the treated area

These effects are usually mild and short-lived, but they are still worth noting.

Who Should Use Extra Caution

People who should use extra caution include those who:

• take photosensitizing medications
• have light-sensitive conditions
• have a history of skin cancer
• are pregnant and want guidance on whether a specific modality is appropriate

For diagnosed skin conditions or persistent symptoms, it is best to speak with a dermatologist or qualified healthcare professional before starting any form of phototherapy.

Clinical Phototherapy Safety vs. At-Home Device Safety

Clinical phototherapy and at-home phototherapy differ in intensity, oversight, and risk management.

Feature	Clinical Phototherapy	At-Home Phototherapy
Common light type	UV-based protocols	LED red, blue, or near-infrared
Oversight	Medical supervision	Self-directed use
Dose control	Precisely tracked	Depends on user adherence and device design
Typical use	Diagnosed medical conditions	Skin support, acne care, recovery, wellness
Safety profile	Effective but requires monitoring due to cumulative UV exposure	Generally lower risk when devices are well designed and used correctly

At-home LED phototherapy is not a replacement for medical care.

Getting Started with Phototherapy: What to Consider First

The right starting point depends on your goal, your condition, and the type of light involved.

Clinical Route

For diagnosed conditions like psoriasis, eczema, or vitiligo, treatment usually starts in a dermatology setting. Clinical phototherapy often involves narrowband UVB or a similar protocol, with dosing adjusted across sessions.

At-Home Route

At-home phototherapy is usually used for skin support, acne, or recovery. Most devices in this category use LED light, including red, blue, or near-infrared.

Some basic details are worth checking:

• clearly stated wavelengths
• irradiance or output information
• safety certifications
• guidance on treatment distance and session length

Device quality varies quite a bit. Two products can both be labeled “light therapy” and still perform very differently.

Lumaflex Foundations Course: Learning Phototherapy Before You Begin

At some point, most people realize the basics are not the hard part. Applying them is. Wavelengths, device specs, and treatment timing all start to matter once you move past the surface level.

The Lumaflex Foundations Course walks through photobiomodulation, wavelength selection, and how devices are used in practice. It gives you enough context to understand what different setups are actually doing, so you are not relying on guesswork or simplified advice.

It is an educational resource, not a medical training program. You can use it to make more informed, evidence-based decisions before starting or investing in a device.

What to Remember

• Phototherapy refers to the therapeutic use of light wavelengths to influence biological processes.
• It includes multiple modalities, including UV phototherapy, blue light therapy, red light therapy, near-infrared therapy, and bright light therapy.
• Different wavelengths penetrate to different depths and work through different mechanisms.
• UV phototherapy is one of the most established medical uses of light and requires supervision.
• Red and near-infrared LED phototherapy have a growing evidence base, but results vary by device and protocol.
• At-home LED phototherapy can be useful for some goals, but it is not equivalent to clinical phototherapy for diagnosed conditions.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Clinical phototherapy, especially UV-based treatment, requires medical supervision. If you have a diagnosed skin condition or ongoing symptoms, consult a qualified dermatologist before starting any form of phototherapy.

References

Almutawa, F., Alnomair, N., Wang, Y., Hamzavi, I., & Lim, H. W. (2013). Systematic review of UV-based therapy for psoriasis. American Journal of Clinical Dermatology, 14(2), 87–109. https://link.springer.com/article/10.1007/s40257-013-0015-y

Ash, C., Harrison, A., Drew, S., & Whittall, R. (2015). A randomized controlled study for the treatment of acne vulgaris using high-intensity blue light. Journal of Cosmetic and Laser Therapy, 17(5), 259–264. https://doi.org/10.3109/14764172.2015.1027227

Avci, P., Gupta, A., Sadasivam, M., Vecchio, D., Pam, Z., Pam, N., Hamblin, M. R. (2013). Low-level laser (light) therapy (LLLT) in skin: Stimulating, healing, restoring. Seminars in Cutaneous Medicine and Surgery, 32(1), 41–52. https://pmc.ncbi.nlm.nih.gov/articles/PMC4126803/

Hamblin, M. R. (2017). Mechanisms and applications of the anti-inflammatory effects of photobiomodulation. AIMS Biophysics, 4(3), 337–361. https://doi.org/10.3934/biophy.2017.3.337

Huang, Y. Y., Chen, A. C. H., Carroll, J. D., & Hamblin, M. R. (2009). Biphasic dose response in low level light therapy. Dose-Response, 7(4), 358–383. https://doi.org/10.2203/dose-response.09-027.Hamblin

M.Hauptman, A.El Othmani, S.Pazhyanur, and M.Nakamura, “Narrowband-Ultraviolet B Phototherapy for Psoriasis Treatment in Skin of Color: A Systematic Review and Meta-Analysis,” Photodermatology, Photoimmunology & Photomedicine41, no. 5 (2025): e70051, https://doi.org/10.1111/phpp.70051.  

Papageorgiou, P., Katsambas, A., & Chu, A. (2000). Phototherapy with blue (415 nm) and red (660 nm) light in the treatment of acne vulgaris. British Journal of Dermatology, 142(5), 973–978. https://doi.org/10.1046/j.1365-2133.2000.03481.x

Wirz-Justice, A., Benedetti, F., & Terman, M. (2013). Chronotherapeutics for affective disorders: A clinician’s manual for light and wake therapy. Karger. https://doi.org/10.1017/s003329170500437x

Yadav, A., et al. (2017). Effect of low-level laser therapy on wound healing: A systematic review. Photodermatology, Photoimmunology & Photomedicine, 33(4), 181–192.  Taha, N., Daoud, H., Malik, T., Shettysowkoor, J., & Rahman, S. (2024). The Effects of Low-Level Laser Therapy on Wound Healing and Pain Management in Skin Wounds: A Systematic Review and Meta-Analysis. Cureus, 16(10), e72542. https://pmc.ncbi.nlm.nih.gov/articles/PMC11602420/