Helping People Achieve Clear Skin Since 2007

Helping People Achieve Clear Skin Since 2007


Can Light Really Treat Acne? The Truth About Photodynamic Therapy

By Dr. Jaggi Rao, MD, FRCPC, Double board-certified dermatologist

Photodynamic therapy is a tool for treating acne that utilizes the interactions of certain wavelengths with acne bacteria and the skin itself. Blue light kills acne bacteria on the skin. Red light heats and shrinks oil-producing sebum glands in the skin. And the use of red and blue in a pulsating, photodynamic acne treatment system minimizes the risk of accidental overheating or burning of the skin. But light treatment is never enough all by itself to get rid of acne for good.

photodynamic therapy for acne
Blue light therapy can kill acne bacteria in 48 hours or less.


  • Photodynamic therapy for acne takes advantage of the effects of certain wavelengths of light on bacteria and on the skin.
  • Visible blue light can damage the cell membranes of acne bacteria, killing them in 48 hours or less.
  • Blue light may not reach the bottom of skin pores, but it is never necessary to kill all acne bacteria to clear up a blemish. A few acne bacteria on the skin are actually beneficial, since they consume excess oil.
  • Red light reaches below the pores to heat oil-producing sebaceous glands, reducing oil production in the skin.
  • How soon your blemishes clear depends on how fast your skin heals itself after acne bacteria are gone. Teens may see results overnight, while adults may not see results for a week or more.
  • Non-white skin types respond well to a combination of pre-treatment and blue light therapy.

How Blue Light Can Treat Acne

For centuries, acne sufferers were advised to let the sun “dry out” their acne. It turns out that it is never a good idea to use the sun or anything else to dry out the skin to treat acne, because dry skin is tight skin, and tight skin traps sebum and bacteria in pores. The visible blue light from the sun, however, actually does treat acne by killing acne bacteria.

Acne bacteria have chemicals in their protective membranes called porphyrins. One of the poryphorins in the protective barrier of the acne bacterium resonates with visible blue light of wavelengths between 407 and 420 nanometers. These blue pigments in the bacteria respond to the blue light in a photodynamic fashion that causes them heat up and burst the membrane. Oxygen from the surrounding pore attacks the organelles inside the bacterium, and most acne bacteria, about 99.99% of all acne bacteria, die within 48 hours of exposure.

Blue light therapy has a tremendous advantage over antibiotics since bacteria cannot develop genetic resistance to the therapy, and the treatment will not create a resistant strain. Even better, the skin itself is undamaged by these wavelengths of light. UV light is not necessary to kill the bacteria.

Killing acne bacteria does not clear up blemishes instantly. Bacteria do not actually cause inflammation in the pore. The immune system’s over-reaction to the presence of bacteria is what causes itching, irritation, and, at least in part, hardening of sebum. When the bacteria die, their stimulation of the immune system stops, and the blemish can begin to heal. The skin of teenagers and young adults, however, can begin to heal within 48 hours of blue light treatment. Daily cleansing will keep blemishes away once the skin has cleared.

How Red Light Can Heal Acne

Bacteria and the immune system’s reaction to them is only part of acne. Another part of the problem is the over-production of sebum. Stopping the over-production of sebum can help the skin keep pores open.

The sebaceous glands that make sebum are located beneath the pores. They cannot be reached by blue light. They can, however, be reached by red light. When the skin is irradiated with visible red light, sebaceous glands are heated, and shrink. Although it is possible to irritate the skin so much that there is a rebound reaction in which pores actually fill with even more sebum, a mild dose of red light may be just enough to stop the production of new whiteheads and blackheads.

Pulsing Blue and Red Light

To prevent skin damage by red light treatment, dermatologists have devised treatment devices that deliver pulses of blue and red light. The idea is to heat the lower layers of the skin just enough to reduce oil production without damaging the skin.

Just How Good Is Photodynamic Therapy?

It is very rare for any acne treatment to be completely successful. Most studies comparing photodynamic therapy find that it gets rid of about half of whiteheads and blackheads and about 2/3 of pimples after a month of weekly treatments. Benzoyl peroxide, by comparison, is usually about 50% as successful. But should everyone use light therapy no matter what their skin type?

Here are some important considerations:

  • If you can’t take Accutane or Retin-A because you are a woman who wants to become pregnant or who is pregnant, consider blue light therapy first.
  • Never use photodynamic therapy at home when you are sleepy or when you are taking a nap. There is a possibility of burning your skin, and the blue light from the therapy unit will keep your brain from making its own sleep-inducing melatonin, at least while the light is on.
  • Blue light therapy is probably the first antibacterial treatment you should try if you have an African skin type. It will not cause irritation or pigmentation that most other antibacterial skin products will on African skin.
  • Blue light therapy only gets rid of acne bacteria. If you are using acne care products that contain harsh detergents or stinging alcohol, blue light therapy won’t do anything to correct their effects on your skin.
  • Blue light therapy tends to work best on Asian skin types if they are pretreated with another bacteria-fighting treatment. For instance, if you have Asian skin, you might pre-treat your skin with the mildest available benzoyl peroxide lotion, absolutely nothing stronger than 2.5%. Then, if there is no irritation to your skin, do a blue light treatment the next day, making sure you have not used benzoyl peroxide for at least 24 hours before you do the blue light treatment.
  • Red light therapy tends to work best on dark brown and black skin, but it is important not to overheat the skin. Overheating brown and black skin can trigger a reaction that increases the production of pigment in the skin. If your red light therapy feels hot, stop it. It has already done enough work. People who have African skin types usually respond best to pulsating light therapy.
  • Your dermatologist may recommend a pre-treatment with 5-aminolevulenic acid (one of many compounds known by the abbreviation ALA) before using blue light. This is especially useful for persons who have Korean skin types.
  • If you use a home blue light, red light, combination light, or pulsating light system, keep in mind that more is not better. You won’t get better results by holding your face close to the lamp. This may kill bacteria, but it will injure your skin in ways that it repairs by making even more oil.
  • Photodynamic treatment is always just a small part of acne skin care. The most efficient way to perform other needed skin care tasks is to use an acne treatment system, such as Exposed Skin Care.
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