Intranasal photobiomodulation: principles and scientific research

What is intranasal photobiomodulation?

Intranasal photobiomodulation applies low-intensity red or near-infrared light to the nasal cavity. In the commonly described non-invasive method, a small light source sits at the entrance to the nose, illuminating mainly the accessible tissues around the applicator. Research explores local mucosal responses and possible responses beyond the illuminated area. [2]

The nasal mucosa has a rich blood supply, and the nasal cavity lies close to certain nervous system structures. These anatomical relationships explain researchers’ interest. On their own, however, they do not establish where a biologically effective light dose will reach or what the outcome will be. We need to distinguish local effects on the mucosa, possible indirect effects and direct delivery of light to nervous tissue. Each possibility requires its own evidence. [2] [3]

Intranasal, intravenous and transcranial applications: what is the difference?

The same wavelength therefore does not mean the same dose in the blood or brain. Findings from one method cannot automatically be transferred to another. The article Laser blood irradiation: methods and research also explains the basic terminology. [2] [3]

Lew Lim and the development of the research concept

In The Potential of Intranasal Light Therapy for Brain Stimulation, presented at the NAALT conference on 2 February 2013, Lew Lim described a shift from an interest in blood irradiation towards possible neurological effects. He connected earlier publications with device development and user observations. This is a historical development and conference document, not a randomised clinical trial. [1]

Such a document helps explain how the concept emerged and why different wavelengths and pulse settings later attracted interest. However, measurements and appropriately controlled research are needed to assess the effectiveness of a particular method. The original technical proposal and user experiences cannot replace them.

Three possible levels of response to light

1. A local response in the nasal mucosa

Light first acts in the tissue that absorbs it. Researchers study cellular and vascular responses in and around the mucosa, as well as changes in local symptoms. Research into nasal patency in allergic rhinitis is one example. A change in the nose does not, by itself, demonstrate an effect on a brain disorder. [6]

2. Indirect effects through blood and regulatory signals

The review by Salehpour and colleagues also considers whether a local stimulus could trigger a response beyond the illuminated area. In this context, blood properties, vascular responses, neural pathways and other signalling routes are discussed. Their contribution to any clinical outcome still needs to be clarified. [2]

Assessing this hypothesis requires following the whole chain: did a blood measurement change, did blood flow to the target tissue change, and did this bring a measurable benefit to the person? One part of this sequence does not automatically establish the others. The article Thick blood, viscosity and microcirculation explains blood properties in more detail.

3. Direct penetration of light towards brain tissue

In 2019, Cassano and colleagues used a computer model to compare light propagation from different locations on the head and inside the nose. Source position substantially affected the estimated amount of energy reaching target regions. A source near the roof of the nasal cavity produced a different light distribution from one at the nasal entrance. This was a dosimetry model, not clinical evidence of improved memory or mood. [3]

In this model, positioning the source at the nasal entrance resulted in very little direct light delivery to the brain regions studied. Light is absorbed and scattered along its path. The findings depended on the model’s assumptions and the source’s position and parameters; they are not a universal measurement of every nasal applicator. [3]

Why do dose and applicator position matter?

The energy emitted by a diode differs from the energy absorbed by the target tissue. Power per unit area, exposure time, wavelength, pulses, applicator position and individual anatomy all matter. A single number on a device therefore cannot establish effectiveness for a particular diagnosis. [3]

Differences between cells also matter. Mature human red blood cells have no mitochondria, so any response they show cannot be explained by directly stimulating mitochondria inside them. Membrane-related and indirect mechanisms are also considered when discussing blood. The article Cells and photobiomodulation explains the context in more detail.

The research parameters reported in studies help readers compare methods. They are not a universal guide to dosing at home. We are also preparing a separate article on Photobiomodulation and the right light dose.

What do clinical studies show?

The following studies investigated different groups of people, procedures and outcomes. They cannot therefore be combined into one general claim about the effectiveness of nasal light.

Nasal application alone and blood measurements

In 2012, Liu and colleagues described a randomised, double-blind, placebo-controlled study involving 90 patients with coronary heart disease or cerebral infarction. Sixty received nasal laser application at 650 nm, while thirty received a control procedure with no light output. In the active group, the authors reported decreases in measures including total and LDL cholesterol, plasma viscosity and red blood cell aggregation. [7]

Interpretation needs to account for differences in baseline values and analyses largely based on before-and-after comparisons within each group. A significant change in one group and a non-significant change in the other do not, by themselves, demonstrate a significant difference between groups. The study did not measure improvements in memory or vision, or a reduction in vascular events, and did not test KINGRAY Light. [7]

Dementia and combined application

In 2017, Saltmarche and colleagues followed five people with dementia or Alzheimer’s disease during a 12-week programme combining transcranial and intranasal application. They used 810 nm LED light pulsed at 10 Hz. Favourable changes in cognitive tests were observed, but without a control group, neither the cause of improvement nor the separate effect of the nasal component can be reliably established. [4]

The study was sponsored by Vielight, which supplied the devices. Some authors disclosed paid consulting or roles within the company. The results support further controlled research; they do not establish the effectiveness of every nasal device. [4]

Cognitive difficulties after COVID-19

A randomised, double-blind pilot study published in 2026 enrolled 43 adults with cognitive difficulties after COVID-19; 41 were analysed. It combined head and nasal illumination using 810 nm light pulsed at 40 Hz. After eight weeks, the primary cognitive outcome did not reach statistical significance: between-group difference 0.043; 95% confidence interval −0.007 to 0.092; p = 0.088. [5]

Favourable findings appeared in the younger subgroup and in some attention measures. The subgroup analyses were exploratory, with no adjustment for multiple comparisons. Fatigue and mobility outcomes favoured the control group. No serious adverse events were reported. The research was funded by the manufacturer, Vielight; all authors disclosed remuneration from the company. The effect of nasal application alone was not isolated. [5]

Allergic rhinitis and local effects

In 2025, Oliveira and colleagues published a blinded randomised study involving 62 patients with allergic rhinitis: 33 in the active group and 29 in the control group. The protocol combined internal and external nasal illumination and included eight sessions over one month. The abstract reports improvements in some measures of nasal patency and symptoms, with no significant change in the smell identification test. [6]

This investigated a local indication. It does not demonstrate treatment of dementia or establish the effectiveness of a nasal clip used alone with a different protocol. This section is based on the available abstract, not the full study text.

Why does a comparison group matter?

If someone feels better while using a device, their experience matters. However, an appropriate comparison is needed to help explain what caused the change. Fluctuating symptoms, concurrent care, expectations and repeated testing can all play a role. Random allocation and a credible inactive device reduce the risk of attributing these influences to the light itself.

With combined procedures, the contribution of each component also needs to be distinguished. Comparing head illumination, nasal application alone, their combination and a control would help determine what each route adds. Without this distinction, the separate effect of the nasal component remains uncertain.

What can we say, and what remains open?

The nasal mucosa is an accessible site for studying local and possible distant biological responses to light. Research so far includes nasal symptoms, blood measurements and combined neurological protocols. Each group of findings needs to be assessed according to the method used and what was actually measured. [4]–[7]

These studies justify further research. They do not establish that every nasal applicator reliably improves brain microcirculation or treats neurological disorders. Even good short-term tolerability in a small study provides limited information about long-term safety.

The deep placement of a light source within the nasal cavity investigated in models is not an instruction for home use. A particular device must be used according to its intended purpose and instructions; health concerns require professional assessment. A research model should not be treated as a procedure for a standard nasal clip. [3]

How do the other articles connect?

The existing articles on cells and photobiomodulation and blood viscosity and microcirculation build on these explanations of the principles.

We are preparing separate articles on Memory, dementia and photobiomodulation, Photobiomodulation and the right light dose, and Light, cholesterol and blood lipids. Links will be added after publication.