Blue light is a type of electromagnetic radiation with a wavelength of approximately 400-490 nanometers (nm, one billionth of a meter) on the visible light spectrum. It is used in various applications, including medical treatments and disinfection procedures. Recent studies have shown that blue light in the 460-470nm range can be an effective tool in killing bacteria.

There are about 30,000 known species of bacteria.  Some are pathogenic (cause disease) while some are “friendly” and play an important role in microbiomes such as in the gut and on the skin.  For example, Lactobacillus and Bifidobacteria and Bacteroides thetaiotaomicron help you digest food in the gut, and on the skin S. epidermidis helps protect the skin from water loss and damage.  The presence of these friendly bacterial strains helps guard against colonization of harmful bacteria like E. coli in the gut and Staph aureus on the skin.

As we know, bacteria are abundant everywhere, especially where there are high concentrations of humans:  hospitals, clinics, schools, offices and homes.  And obviously, anything that is meant to be touched (handles, doorknobs, keyboards, childrens toys, etc.) has a much higher bacterial count.

The spread of bacteria can be controlled by using antibiotics and disinfectants. However, the overuse of antibiotics has led to the development of antibiotic-resistant strains of bacteria, making it more challenging to treat infections. In addition, some disinfectants are harmful to humans and the environment.  Fortunately, there are other means to fight harmful bacteria.

Blue light therapy has emerged as an alternative to traditional methods of bacterial control. Research has shown that blue light in the 470nm range can effectively kill bacteria, including some antibiotic-resistant strains, without causing harm to human cells or the environment.

How does blue light kill bacteria?

Blue light at a wavelength of 470nm has been found to be effective in killing bacteria due to its ability to penetrate the bacterial cell membrane and cause damage to the bacterial DNA. Bacteria contain a molecule called porphyrin, which is sensitive to light. When blue light at a wavelength of 470nm is applied to the bacteria, the porphyrin molecule (the photosensitizer in the image below) absorbs the light energy and produces reactive oxygen species (ROS).

ROS are highly reactive molecules that can cause damage to bacterial DNA, proteins, and cell membranes. ROS can also interfere with bacterial metabolism, leading to the destruction of the bacterial cell. The production of ROS by the porphyrin molecule in response to blue light is known as photodynamic inactivation (PDI).

from Antimicrobial Blue Light versus Pathogenic Bacteria: Mechanism, Application in the Food Industry, Hurdle Technologies and Potential Resistance. Joshua Hadi, Shuyan Wu, and Gale Brightwell. Foods. 2020 Dec; 9(12): 1895.

PDI using blue light at 470nm has been shown to be effective in killing a wide range of bacteria, including Staphylococcus aureus, Escherichia coli (E.coli), and Pseudomonas aeruginosa. In addition, studies have shown that blue light at this wavelength can kill some antibiotic-resistant strains of bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE).

Applications of blue light therapy for bacterial control

Blue light therapy has a wide range of applications for bacterial control. It can be used in hospitals and clinics to disinfect surfaces, medical equipment, and patient rooms. Blue light therapy can also be used in the food industry to disinfect food products and equipment.

In dentistry, blue light therapy has been used to kill bacteria associated with dental caries and periodontal disease. It has also been shown to be effective in reducing the bacterial load in root canals.

Blue light therapy has also been used in the treatment of acne. Acne is a skin condition that is caused by the overgrowth of Propionibacterium acnes, a type of bacteria that is found on the skin. Blue light therapy at a wavelength of 470nm has been shown to be effective in killing P. acnes bacteria, reducing inflammation, and improving acne symptoms.  Cellulitis, impetigo, and folliculitis are other skin conditions involving pathogenic bacteria that can also be treated with blue light.

Blue light therapy has been used to treat infected wounds. Infected wounds can be difficult to treat, and antibiotic-resistant strains of bacteria can make the treatment even more challenging. Blue light therapy has been shown to be effective in reducing the bacterial load in infected wounds, promoting wound healing, and reducing the need for antibiotics.   If you have an open wound, it would probably best to use a combination of a topical antiseptic and blue light.  Apply the blue light directly over the wound for 10 minutes, 3x/day for four days, as a guideline.  If your injury involved contact with something dirty/unsanitary, then a course of antibiotics would be prudent, as well.

Advantages of blue light therapy for bacterial control

One of the main advantages of blue light therapy for bacterial control is that it is a non-invasive and non-toxic method of disinfection. Unlike traditional disinfectants, blue light therapy does not produce harmful by-products or residues. It is also safe for use around humans.

Now that it is becoming known that blue light can potentially improve acne-causing bacteria, we are starting to see it in consumer health products.  There are handheld devices that emit blue light, along with therapeutic red and infrared light.  These devices are great for small areas, as they focus the light intensely, bathing the pathological bacteria with the blue wavelength and causing those reactive oxygen species to damage them and kill them.

Using blue light to treat middle ear infection.

There are also LED wraps that emit blue light that can be used for treating facial acne and other dermatological conditions related to harmful bacteria.

Using an LED wrap for blue light therapy to treat facial acne

Blue light can improve acne and red blemishes due to staph infection

According to Cedars-Sinai, large, painful bumps that look like acne can sometimes be caused by Staphylococcus aureus, which lives on our skin, in our noses, and on surfaces everywhere.  Inflamed/ reddish skin blemishes are a sign of staph infection and should be treated before they have a chance to spread.

The LED wrap shown above emits blue light, which can be used for treating acne and staph-related skin blemishes.  It can also emit red light, which happens to have the opposite effect.  It stimulates collagen and elastin production and reduces fine wrinkles, and basically increases cell energy and metabolism.

In the video below, I go into more detail on the therapeutic benefits of blue light.