Blue Light Therapy for Precancers: How It Works and What to Expect

Learn what to expect from blue light therapy for precancers. Blue light therapy treats cancer and precancers.

Blue light therapy is a form of phototherapy used to treat a variety of skin conditions such as sun-damaged skin, acne vulgaris, and actinic keratosis (precancerous lesions). It is commonly used with a light-sensitive medication, commonly referred to as photodynamic therapy (PDT), for cancer treatment to target precancerous and early-stage skin cancer lesions.

An actinic keratosis, also known as solar keratosis, is a precancerous skin lesion. It develops as a result of too much exposure to ultraviolet (UV) radiation from the sun or from indoor tanning.

Actinic keratosis may eventually evolve into a skin cancer known as squamous cell carcinoma if left untreated. It generally presents as a crusty scaly growth on sun-exposed areas such as the face, shoulders, and arms.[1]


How Blue Light Treatment Works


Prior to exposing the skin to blue light, a light-sensitive medication is applied topically to the targeted area.[2] The medication is only activated when specific colors of light (such as blue or red light) is shined upon the targeted area. Generally, for the treatment of actinic keratosis, a topical light-sensitive medication called aminolevulinic acid (ALA) is used. Once ALA is absorbed by the skin, it is converted into the light-sensitive molecule porphyrin.[3] ALA is applied in advance and left on the skin for at least an hour or up to many hours so that the medication can be absorbed into the skin. Because precancerous cells naturally divide more quickly than healthy cells, these cells are quicker at metabolizing the ALA into the light-sensitive porphyrin. Therefore, the precancerous actinic keratosis cells are more sensitive to blue light than the surrounding healthy cells, making blue light therapy an effective cancer treatment.

In photodynamic therapy, blue light activates the light-sensitive molecule porphyrin to generate reactive byproducts known as reactive oxygen radicals. The reactive oxygen radicals disrupt cellular activity resulting in cell death.[4] Limiting the duration of the light source allows for the blue light to more specifically target the precancerous actinic keratosis cells.


After the treatment, the treated skin will be extremely sensitive to blue light and sunlight for the next 48 hours and avoidance of light is required to protect the skin.[4] Helpful tips to reduce sun exposure include:

  • Wearing a hat
  • Wearing protective clothing (ie. Long-sleeved shirts, pants, or gloves for hands)
  • Staying indoors

Continued use of sunscreen is always good practice for skin health in general, but sunscreen will not protect the skin from blue light. Therefore, sunscreen alone will not protect the skin after treatment,


Blue light therapy serves as an alternative treatment for actinic keratoses and has several advantages, including:

  • Non-invasiveness
  • Little to no scarring
  • Quick recovery time
  • Quick procedure[2]


Side Effects and Potential Complications

Patients commonly note discomfort and pain during light therapy. Common side effects following the treatment are redness, swelling, tenderness, and blisters may form in some people.[5] The treated area may crust over, causing the skin to peel; however, if this occurs, most patients heal within 1 to 2 weeks.

Blue light therapy is not indicated for people that already have a disease that causes light sensitivity such as systemic lupus erythematosus and porphyria.[5]

* This Website is for general skin beauty, wellness, and health information only. This Website is not to be used as a substitute for medical advice, diagnosis or treatment of any health condition or problem. The information provided on this Website should never be used to disregard, delay, or refuse treatment or advice from a physician or a qualified health provider.


  1. Lebwohl MM, Sarnoff DSM. Actinic Keratosis (AK). Link to research.
  2. Brown SB, Brown EA, Walker I. The present and future role of photodynamic therapy in cancer treatment -. Lancet Oncology. 2004; 5(8):497-508; PMID: Link to research.
  3. Triesscheijn M, Baas P, Schellens JHM, et al. Photodynamic Therapy in Oncology. The Oncologist. 2006; 11:1034-1044; PMID: Link to research.
  4. Huang Z. A Review of Progress in Clinical Photodynamic Therapy. Technology in Cancer Research Treatment. 2005; 4(3):283-293; PMID: 15896084 Link to research.
  5. Wan MT, Lin JY. Current evidence and applications of photodynamic therapy in dermatology. Clinical, Cosmetic and Investigational Dermatology. 2014; 7:145-163; PMID: Link to research.