Red Light Therapy for Immune System

“Boost your immune system with red light therapy” is one of the most common claims in the PBM marketing world. It sounds appealing — who would not want a stronger immune system? But the claim is misleading in several ways, and the reality is more nuanced and more interesting than simple “immune boosting.”

This page explains what PBM actually does to the immune system, why “boosting” is the wrong framework, what the evidence shows for infection recovery, and why COVID-era claims were largely unfounded.

Why “immune boosting” is the wrong concept

The immune system is not a single entity that can be turned up or down like a volume dial. It is a complex network of cells, signalling molecules, organs, and barriers that must maintain a precise balance:

Too little activity = susceptibility to infections, poor wound healing, increased cancer risk
Too much activity = autoimmune disease, chronic inflammation, allergies, cytokine storms

A healthy immune system does not need “boosting.” It needs to respond appropriately — activating strongly against genuine threats (pathogens, cancer cells) and standing down when the threat is eliminated or when it encounters the body’s own tissues.

PBM does not simply “boost” the immune system. The evidence suggests it modulates immune function — shifting the balance rather than uniformly increasing activity. This distinction matters enormously, and anyone selling you PBM as an “immune booster” is oversimplifying to the point of inaccuracy.

What PBM actually does to immune cells

Effects on macrophages

Macrophages are versatile immune cells that engulf pathogens, present antigens to other immune cells, and produce inflammatory mediators. They exist on a spectrum between two functional states:

M1 (classically activated): Pro-inflammatory, antimicrobial, tumoricidal
M2 (alternatively activated): Anti-inflammatory, tissue repair, immunoregulatory

PBM has been shown to influence macrophage polarisation. In inflammatory conditions, PBM tends to shift macrophages towards the M2 phenotype, reducing inflammation and promoting repair (Fernandes et al., 2015). In contexts of infection or tissue damage, this shift could be beneficial for resolution and healing — but could also theoretically reduce the antimicrobial M1 response.

Effects on T lymphocytes

T cells are central coordinators of adaptive immunity. PBM has been shown to:

Modulate T helper cell differentiation — Influencing the balance between Th1, Th2, and Th17 subsets (Choi et al., 2012)
Promote regulatory T cell (Treg) activity — Tregs suppress excessive immune responses and maintain self-tolerance. Enhanced Treg function is beneficial in autoimmune conditions but could theoretically reduce anti-pathogen responses
Affect T cell proliferation — Some studies show increased proliferation, others decreased, depending on dose and timing (the biphasic response)

Effects on neutrophils

Neutrophils are the first responders to infection and tissue damage. PBM has been shown to modulate neutrophil function, including:

Altered reactive oxygen species (ROS) production
Modified chemotaxis (movement towards infection sites)
Changed degranulation patterns

Again, the direction of these effects depends on dose, wavelength, and the inflammatory context. PBM does not simply “supercharge” neutrophils.

Effects on natural killer (NK) cells

NK cells kill virus-infected cells and tumour cells without prior sensitisation. Limited evidence suggests PBM can increase NK cell cytotoxicity, which could theoretically improve anti-viral and anti-tumour surveillance (Rodrigo et al., 2009). However, the clinical significance of this in humans is unknown.

Effects on inflammatory mediators

This is the best-characterised immune effect of PBM:

Reduces: TNF-alpha, IL-1beta, IL-6, IL-8, prostaglandin E2, COX-2 expression
Increases: IL-10 (anti-inflammatory), TGF-beta (regulatory)
Modulates: NF-kappaB signalling, a master regulator of inflammatory gene expression

These effects are consistent across hundreds of studies and represent the primary mechanism by which PBM reduces pain and inflammation in conditions like arthritis, tendonitis, and wound healing.

PBM and infection recovery

The theoretical basis

If PBM modulates immune function and reduces excessive inflammation, could it help recovery from infections? The rationale has two components:

Reducing immunopathology — Many of the symptoms and tissue damage during infection are caused not by the pathogen itself but by the immune response. Excessive inflammation (cytokine storms, neutrophil-mediated tissue damage) worsens outcomes in pneumonia, sepsis, and severe viral infections. PBM’s anti-inflammatory effects could theoretically reduce this collateral damage.
Supporting tissue repair — PBM accelerates wound healing and tissue repair. After an infection has been controlled, faster recovery of damaged tissue would be beneficial.

What the evidence shows

Wound infections: PBM has moderate evidence for improving healing of infected wounds, primarily through reducing inflammation and stimulating tissue repair rather than directly killing pathogens (though antimicrobial photodynamic therapy — a related but different approach — does directly kill bacteria using photosensitisers).

Upper respiratory infections: No controlled human trials have examined PBM for common colds, influenza, or other respiratory infections. There is no evidence that PBM prevents or shortens respiratory infections.

Post-surgical infections: Some evidence suggests PBM reduces post-surgical inflammation and may lower infection risk through improved tissue integrity, but this is primarily about tissue quality rather than immune “boosting.”

The COVID question

During the COVID-19 pandemic, multiple claims emerged about red light therapy and coronavirus:

What was claimed

Red light therapy could prevent COVID-19 infection
PBM could treat active COVID-19
Red light therapy could reduce cytokine storm severity
Near-infrared light could “kill” the virus

What the evidence actually showed

Prevention: There is no evidence that PBM prevents SARS-CoV-2 infection. Viral entry depends on ACE2 receptor binding and viral load exposure. PBM does not affect either.

Treatment of active infection: No controlled trial demonstrated that PBM improved outcomes in COVID-19 patients. A few case series and small, poorly controlled studies reported some benefit, but these were insufficient to draw conclusions and were often published in low-quality journals.

Cytokine storm modulation: The theoretical argument that PBM could reduce the cytokine storm in severe COVID was biologically plausible — PBM does reduce inflammatory cytokines in other contexts. However, severe COVID cytokine storms are a medical emergency requiring ICU-level care. Suggesting PBM as an alternative to established critical care interventions was irresponsible.

Viral inactivation: Claims that red or near-infrared light could “kill” SARS-CoV-2 were based on misunderstanding. UV-C light (200–280nm) can inactivate viruses on surfaces, but UV-C is not red light therapy, is not safe for human tissue exposure, and is an entirely different technology.

Bottom line on COVID: The pandemic produced a wave of unfounded PBM claims that damaged the credibility of the legitimate photobiomodulation research community. There is no evidence that red light therapy prevents, treats, or cures COVID-19.

A reasonable protocol

If you wish to use PBM as part of a general health maintenance approach (without specific “immune boosting” expectations):

Wavelength

660nm (red) and 850nm (NIR) — The most commonly studied wavelengths for systemic PBM effects

Application

Full-body or large-area exposure — Panels positioned at torso height, 15–30cm from the body
Some practitioners suggest targeting the thymus area (upper chest) or lymph node regions (neck, axillae, groin), but there is no specific evidence that targeting these areas produces superior immune effects

Dosage

10–20 J/cm² at the skin surface
10–15 minutes per session, depending on device output

Frequency

3–5 times per week for general wellness use

Realistic expectations

PBM may modestly support recovery from illness or injury through anti-inflammatory and tissue-repair effects
It will not “supercharge” your immune system or protect you from specific infections
The fundamentals matter far more: sleep, nutrition, exercise, stress management, vaccination, hand hygiene

The bottom line

Red light therapy interacts with the immune system — that much is well established. But it modulates rather than simply boosts, and the direction and magnitude of its effects depend on dose, timing, and the individual’s immune state.

The evidence does not support using PBM to prevent infections, treat acute illness, or replace any established medical intervention. It may offer modest benefits for recovery and inflammation management, consistent with its effects on other body systems.

Be deeply sceptical of any product marketed as an “immune-boosting light therapy device.” The immune system does not need boosting — it needs balance. And the evidence that PBM achieves clinically meaningful immune improvements in healthy people is, frankly, not there.