Photobiomodulation (PBM) / LLLT

There are many types of devices with varying energy output. Some devices can be purchased directly by consumers, and others are for use only in the doctor’s clinic. Despite of the increase of such devices in the market today, important questions regarding dosing and efficacy remain unanswered.

Photobiomodulation (PBM), also called low level laser therapy (LLLT), is a treatment method used to stimulate the growth of hair follicles. It is often used in conjunction with other hair loss treatments. Some patients benefited, but some did not. There are many types of devices with varying energy output. Some devices can be purchased directly by consumers, and others are for use only in the doctor’s office. Despite the increase of such devices in the market today, important questions regarding dosing and effectiveness remain unanswered. Consumers must be aware of these unanswered questions in order to make an informed decision. I suggest you to seek the advice of a hair loss specialist who is familiar with the various types of hair loss and the various options for treating them properly and effectively.

The answer is that there is a lot we do not know about optimal wavelengths and dosing of PBM treatment to treat hair loss. Despite the work done, important questions are remained unanswered. It is recommended that all treatments and options be reviewed with a hair loss specialist before deciding to purchase an OTC device to treat hair loss.

Researchers are not sure how PBM works to stimulate hair growth, but they believe that it should stimulate hair to the growth phase (anagen re-entry), prolongation of the growth cycle (anagen elongation), active hair growth. It has been suggested that the drug, which is thought to cause hair loss in androgenic alopecia (AGA), has an effect on modulating alpha reductase activity (the enzyme that converts testosterone to dihydrotestosterone (DHT)). Research is ongoing to further determine cellular targets and mechanisms of action for hair growth stimulation, as this will help researchers to determine optimal wavelengths and dosing.

The short answer is probably, but it may not yet be available on current devices. Some researchers believe that the chromophore responsible for PBM response in hair growth stimulation is the Cytochrome C oxidase found in the mitochondria. Tissue culture experiments showed peak DNA production in the 4 wavelength range, felt as a reflection of Cytochrome C oxidase activity: 614-624nm; 668-684n, 751-772nm and 813-846nm. (ref 1, 6) A more recent study specific to hair growth evaluated the response of various wavelengths in the shaved backs of Sprague-Dawley rats using 632, 670, 785 and 830nm diodes. The higher wavelengths of 830 nm and 785 nm had a significant effect on hair growth stimulation where 830 nm was most effective (ref Lasers Med Sci).

Interestingly, none of the currently marketed devices use wavelengths of 694 nm, 785 nm, or 830 nm. Lower wavelengths ranging from 635nm to 650nm and 655nm have been used at 678nm until most of the devices deleted by the FDA in the USA. The reasons for this have little to do with the previously mentioned scientific studies, and everything to do with the cost of the FDA’s pre-market approval (PMA) versus 510K clearance for low-risk medical devices. The impact of the regulatory process on device development will be discussed further below. Importantly, human review shows that results from some of these available devices have a hair growth benefit for some patients. However, closer examination raises questions about the methodology and whether the study results can be applied in real use environments.

Important optical parameters for PBM include wavelength as well as radiation or power density (mW / cm2) – where the light is bright, the distance to the target from the light source, and the frequency and time the light is applied to the head / scalp (3 times a week for 20 minutes); as well as the duration or course of therapy (6 months, 12 months, etc.). Determining the optimal dosage is particularly important given the biphasic dose response, a phenomenon that LLLT is believed to occur in both animals and humans, i.e. too little energy will not respond and too much energy can actually have a detrimental effect on the target.

Researching optimal dosage for hair growth, the researchers conducted a review of 90 published studies and observed a surprisingly wide array of dosage charts and irradiance or power intensities varying by two orders of magnitude, making it impossible to define “optimal” parameters. Also, none of the OTC devices published any justification for their recommended doses, nor did they state why there was no dose adjustment based on Fitzpatrick’s skin type. The final classification has been developed to help determine the dose of skin phototherapy based on the presence of melanin, chromophore in the skin and hair that absorbs laser light.

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