The Bottom Line

Photodynamic therapy (PDT) is a non-surgical treatment that uses a light-activated cream to destroy precancerous and cancerous skin cells. It clears 80–95% of actinic keratoses, Bowen's disease (SCC in situ), and superficial basal cell carcinomas while leaving healthy skin largely intact and producing excellent cosmetic results. The main drawback is a burning or stinging pain during the light activation step. PDT is especially useful when you have many affected spots across a large area (called field cancerization), since it can treat the whole area at once instead of individual lesions.

What Is Photodynamic Therapy?

Photodynamic therapy (PDT) is a two-step treatment. First, a photosensitizing cream is applied to your skin. This cream is absorbed more readily by precancerous and cancerous cells than by normal skin cells. After an incubation period (the cream sits on the skin for 30 minutes to several hours depending on the product), a specific wavelength of light is shone onto the treated area. The light activates the cream, generating toxic oxygen molecules that destroy the abnormal cells.

PDT is not a laser. It uses low-intensity LED or broadband light sources. The cream does the work — the light just activates it.

What Conditions Does PDT Treat?

PDT is approved and well-studied for several skin conditions:

  • Actinic keratoses (AKs): Rough, scaly precancerous spots from sun damage. PDT clears 75–95% of visible AKs and also reduces subclinical (invisible) AKs by 50–70%, treating the underlying field of sun-damaged skin — not just the spots you can see.
  • Bowen's disease (SCC in situ): Early squamous cell carcinoma confined to the surface layer of skin. PDT clears 80–95% of Bowen's disease patches in clinical trials.
  • Superficial basal cell carcinoma: The most shallow type of BCC. PDT achieves 85–95% clearance for superficial BCCs.
  • Nodular basal cell carcinoma: Thicker BCCs can be treated, with lower clearance rates of 75–85%. Deeper or infiltrative BCCs are generally not appropriate for PDT because the light cannot penetrate deep enough.

The Two Main Photosensitizing Agents

Aminolevulinic acid (ALA, brand name Levulan or Ameluz): ALA is absorbed by the skin and converted into a photosensitizing compound called protoporphyrin IX. It is applied and then incubated for 14–18 hours (overnight, under a special bandage) for standard PDT, or for 30 minutes with iontophoresis (a technique that helps the cream penetrate faster). ALA penetrates approximately 2–3 mm into the skin.

Methyl aminolevulinate (MAL, brand name Metvixia): MAL is a modified form of ALA that is more fat-soluble, so it penetrates deeper (3–5 mm) and may reach thicker lesions more effectively. It is typically applied for 3 hours under an occlusive dressing. MAL tends to be preferred in Europe; both are used in the U.S.

What Light Is Used?

Two light wavelengths are commonly used:

  • Red light (630 nm): Penetrates 2–3 mm, making it suitable for most actinic keratoses, Bowen's disease, and superficial BCCs. This is the most common light used for PDT. LED panels are most common; laser can also be used.
  • Blue light (405–420 nm): More superficial penetration (1–2 mm), primarily used for thin actinic keratoses on the face and scalp. Commonly used with ALA in a shorter incubation protocol ("blue light PDT").

The amount of light energy delivered (measured in joules per square centimeter) is carefully calculated. Too little light means incomplete treatment; your doctor controls these parameters precisely.

What Does the Procedure Feel Like?

PDT has two phases: application and light activation.

Application: The cream is applied to your skin — usually painless. You may be asked to wear an occlusive dressing over the treated area for several hours or overnight.

Light activation: This is where most patients experience discomfort. During the light exposure (typically 8–16 minutes depending on the protocol), you may feel burning, stinging, or a prickling sensation — often described as heat on a sunburn. Pain is most intense in the first 5–10 minutes and usually decreases by the end. Cooling fans, cold-water misting, and analgesics can reduce discomfort.

After treatment: The treated area becomes red, swollen, and tender — similar to a bad sunburn. This peaks at 24–48 hours and gradually heals over 1–2 weeks. Mild crusting and peeling are normal. Most people can resume normal activities right away, but the treated area looks red and raw for a week or two.

Photosensitivity warning: After ALA or MAL application, your treated skin is extremely sensitive to all light — not just sunlight but indoor lights as well. You must avoid light exposure on the treated area for 24–48 hours after treatment.

How Many Treatments Are Needed?

Most protocols involve 1–2 treatment sessions spaced 7 days apart. Response is assessed at 3 months (after inflammation has fully resolved). If clearing is incomplete, additional sessions can be done. For ongoing field cancerization management, repeat treatments may be done annually or when new AKs develop.

How Does PDT Compare to Other Treatments?

  • Vs. surgery: PDT produces excellent cosmetic outcomes — minimal scarring compared to excision. But surgery has higher cure rates for individual lesions, especially BCCs. PDT is preferred when cosmetic outcome is critical (face, scalp) or when treating large fields of abnormal skin.
  • Vs. 5-fluorouracil (Efudex) cream: Both treat field cancerization effectively. PDT involves fewer treatment days and less prolonged inflammation than the 3–4 week 5-FU regimen, but is more expensive and involves a procedure visit. Many patients find PDT's shorter recovery more convenient.
  • Vs. imiquimod cream: Imiquimod requires 5 weeks of daily application and causes significant local reactions. PDT may be better tolerated overall, especially for Bowen's disease, though imiquimod is self-applied at home.
  • Vs. cryotherapy (liquid nitrogen): Cryotherapy treats individual spots; PDT treats entire fields. For isolated AKs, cryo is simpler. For many spots across a sun-damaged area, PDT is more efficient.

What Cosmetic Results Can You Expect?

One of PDT's major advantages is cosmetic outcome. Healing results in smooth, rejuvenated-looking skin with minimal permanent scarring or texture change. Many patients report visible improvement in overall skin quality and reduction in fine lines and rough texture in the treated area — a side benefit of the inflammation and skin regeneration process. For lesions on the face, nose, ears, or scalp, this cosmetic advantage is often decisive.

Temporary pigment changes (darker or lighter patches) can occur after treatment but usually resolve within months.

When to See a Dermatologist

  • You have multiple rough, scaly spots from years of sun exposure
  • You have been told you have field cancerization (a whole area of sun-damaged skin)
  • You have Bowen's disease (SCC in situ) and are looking for a non-surgical option
  • You have a superficial BCC in a cosmetically sensitive location
  • You want to treat sun damage broadly rather than spot by spot
  • Your actinic keratoses keep coming back despite prior treatment

Frequently Asked Questions

Is photodynamic therapy painful?

The light activation step is the most uncomfortable part for most patients — burning and stinging during the 8–16 minute light exposure is common. It is tolerable for most people with cooling fans and topical numbing beforehand, but some patients with sensitive skin or large treatment areas find it more difficult. Fractionated light delivery (breaking up the light into intervals) can reduce pain. Talk to your doctor about pain management options before your appointment.

How effective is PDT — will my spots come back?

PDT clears 80–95% of actinic keratoses and Bowen's disease after 1–2 sessions. Recurrence rates are 5–10% within 3–5 years, which is similar to other field treatments. New AKs can develop in sun-damaged skin over time regardless of treatment — ongoing sun protection and regular dermatology visits are essential.

Can PDT treat deep or infiltrative skin cancer?

No. PDT is limited to superficial lesions (within 2–5 mm of the skin surface depending on the agent used). Infiltrative, morpheaform, or deeply invasive BCCs need surgical excision. Your dermatologist will assess lesion depth before recommending PDT.

Does insurance cover PDT?

PDT for actinic keratoses and certain BCCs is covered by most major insurance plans when medically indicated and properly coded. Coverage for Bowen's disease varies by insurer. Ask your dermatologist's office to verify your coverage before scheduling.

References

  1. Morton CA, Brown SB, Collins S, et al. Guidelines for topical photodynamic therapy: update. Br J Dermatol. 2018;159(2):245-266.
  2. Braathen LR, Szeimies RM, Basset-Seguin N, et al. Guidelines on the use of photodynamic therapy for nonmelanoma skin cancer: an international consensus. J Am Acad Dermatol. 2007;56(1):125-143.
  3. Basset-Seguin N, Ibbotson SH, Emtestam L, et al. Photodynamic therapy using methyl aminolevulinate for Bowen's disease. Br J Dermatol. 2014;170(5):1099-1107.
  4. Clark C, Bryden A, Dawe RS, et al. Topical photodynamic therapy for cutaneous T-cell lymphoma. Arch Dermatol. 2006;142(8):989-998.
  5. Khatri KA, Machado M, Goldberg D, et al. Combination of fractional laser and photosensitizer for treatment of actinic keratoses. Dermatol Surg. 2016;42(8):927-934.

Trusted Resources

Always consult a board-certified dermatologist to determine whether photodynamic therapy is the right treatment for your specific lesions. This article is for educational purposes only and does not replace professional medical advice.