Photodynamic therapy, also called blue light therapy, is a medical treatment for actinic keratoses, the precancerous growths caused by sun exposure. A light-sensitizing solution is applied to the whole affected area and then activated with a blue light. Coastal Dermatology + Aesthetics performs it at its San Luis Obispo office.
What photodynamic therapy does
Actinic keratoses are the rough, scaly patches that show up on the parts of you that have taken the most sun: the forehead, the nose, the tops of the ears, the scalp if your hair has thinned, the backs of the hands. They are precancerous, which means some of them go on to become a squamous cell carcinoma if they are left alone. [2] More than 40 million Americans develop them each year. [2]
The usual approach is to freeze the ones you can see, one at a time. That works well when there are a few. When years of sun have left a whole region of skin damaged, freezing spot by spot becomes a game of catch-up, because for every patch you can feel there are usually others that have not surfaced yet.
Photodynamic therapy treats the region instead. A solution is applied across the whole area and absorbed preferentially by the damaged cells. A blue light then activates it, and those cells clear as your skin heals over the following one to two weeks. You come out with new skin across the area rather than a handful of treated spots and the same problem underneath.
What photodynamic therapy is used for
- Actinic keratoses on the face and scalp, treated as a whole area at once
- Sun-damaged regions where new rough patches keep appearing
- Scalps where thinning hair has left skin exposed for years
- People who would rather have two appointments than a standing series of freezing visits
- Reducing the risk that a precancerous growth becomes a skin cancer [1]
Americans develop actinic keratoses each year. If you are finding rough patches that keep coming back, you are in very ordinary company. [2]
How treatment works
The solution goes on
A light-sensitizing solution is applied across the treatment area. It is absorbed much more readily by sun-damaged and precancerous cells than by healthy ones, which is what makes the treatment selective.
You wait, and it concentrates
The solution sits on your skin for around 60 to 90 minutes while it builds up in the cells that need treating. [1] You wait in the office. Bring something to read.
The light activates it
A blue light is then shone across the area. The light reacts with the solution inside those cells, and they clear as your skin heals over the following one to two weeks, leaving new skin behind. [1]
How long the solution sits on your skin before the light. It is the reason this is a longer appointment than most, and the reason it works across a whole area. [1]
Why we treat the whole area, not just the spots you can feel
This is the part worth understanding before you choose between treatments, because it is the whole reason photodynamic therapy exists alongside freezing.
Sun damage does not arrive one spot at a time. It accumulates across a region over years, and the rough patch you can feel today is simply the one that surfaced first. Dermatologists call treating the whole region field treatment, as opposed to lesion-directed treatment, which handles the individual growths you can see.
| Freezing, spot by spot | Photodynamic therapy, whole area | |
|---|---|---|
| What it treats | The growths you and your dermatologist can see and feel | The visible growths and the surrounding damaged skin they came from |
| Best when | You have a small number of scattered patches | A whole region keeps producing new ones |
| Appointment | Quick, often part of a routine visit | Around two hours, most of it waiting |
| Afterward | Small blisters or scabs on each treated spot | 48 hours indoors, then redness and peeling across the area |
| How often | Repeated whenever new patches appear | Usually two treatments, a few weeks apart |
Neither one is better in the abstract. If you have three patches, freezing them is quick and sensible. If you have been back three times in two years and there are always more, treating the field is usually what breaks the cycle. Your dermatologist will tell you which situation you are in, and it is a straightforward conversation.
Areas we treat
Face
Field treatment across the forehead, nose, cheeks and temples, where actinic keratoses cluster.
Scalp
Sun-exposed scalp with multiple patches, which is the area freezing handles least comfortably.
Ears
The tops and rims of the ears, which take decades of sun and are easy to overlook.
Other sun-exposed sites
Used where the selected medication and protocol support it.
Dr. Kilcline is the best dermatologist! Best experience ever! Love her new beautiful facility & location.
The Coastal difference
The examination comes first, and it is the important part
Before any treatment is planned, the area is examined by a board-certified dermatologist. Rough, scaly patches are usually actinic keratoses, and sometimes they are something that needs a different answer entirely. Telling those apart is the work, and it is why this is done in a dermatology practice rather than anywhere a light can be plugged in.
It also means the treatment sits inside a longer view of your skin. Anyone with enough sun damage to need field treatment is someone whose skin is worth watching over time, so photodynamic therapy is usually one part of a plan that includes a skin cancer check and daily sun protection. That plan is what keeps you ahead of it.
Treatments for most patients, with the second given a few weeks after the first. [1] Your dermatologist confirms the number for your skin.
Is it right for you?
Photodynamic therapy is often the right choice if:
- You have several actinic keratoses across one region rather than one or two isolated patches
- New rough patches keep appearing in the same area after freezing
- Your scalp or face has taken decades of sun and the damage is widespread
- You can arrange to stay indoors for the 48 hours afterward [1]
Your dermatologist may suggest something else if:
- You have only a few isolated patches, where freezing is quicker and simpler
- You are taking a medication that makes your skin unusually sensitive to light
- You have a condition that makes light-sensitive treatment unsuitable
- The 48 hours indoors will not fit the next few weeks, in which case it is worth waiting for a week that suits
All of this is settled at your appointment, after your skin has been examined. There is nothing you need to work out in advance.
What to expect afterward
The 48 hours after treatment matter more here than the treatment itself. Your skin stays highly sensitive to light during that window, including daylight through a window or on an overcast day, so you stay indoors and away from bright indoor light. [1] After that, expect redness, some swelling and peeling across the treated area for several days, similar to a strong sunburn, as the treated cells clear and new skin comes through.
In the first 48 hours, do
- Stay indoors and out of daylight completely, including on cloudy days [1]
- Keep the treated area covered if you have to go outside at all
- Use a gentle cleanser and whatever ointment we send you home with
- Plan the treatment for a stretch when two days indoors is easy
In the following week, do
- Let any flaking and peeling come away on its own
- Wear broad-spectrum sunscreen, SPF 30 or higher, every day from then on [3]
- Keep your follow-up appointment, because the second treatment is part of the plan
- Tell us about anything that does not match what we described
Call us about anything severe, worsening or unexpected: significant pain, blistering, spreading redness, or signs of infection. We would far rather hear from you early.
Concerns treated
Sun-damaged and precancerous skin, treated across the whole area. Pick a concern to see how we approach it.
What treatment costs
Photodynamic therapy is a medical treatment rather than a cosmetic one, so the cost depends on the area treated and the number of sessions, and it is handled differently from the aesthetic services on this site. Our office will go through what applies to you before anything is scheduled.
If freezing a few patches would serve you just as well, that is what will be recommended, and it is the less involved appointment of the two.
Appointment length
Around 2 hours, most of it waiting for the solution to take effect
Treatments needed
Usually two, a few weeks apart
Downtime
48 hours indoors, then several days of redness and peeling
Results appear
As the treated skin heals over the following one to two weeks
Photodynamic therapy frequently asked questions
Indoors and away from daylight after treatment. It is the one instruction that really matters, and it is easy when you plan the appointment around it. [1]
Offered at
Both offices offer photodynamic therapy. San Luis Obispo uses blue light and Santa Maria uses red light.
Ready to get it looked at? Request an appointment
Fill out the form below, book online in Santa Maria (opens online scheduler), or give us a call. Cosmetic and aesthetic appointments need no referral. For medical dermatology, we are accepting new patients by referral from your primary care physician; send the referral across and then use the same form.
Sources and medical review
1. American Academy of Dermatology Association. “Actinic keratosis: Diagnosis and treatment.” States that treatment can “reduce your risk of developing skin cancer,” that during photodynamic therapy “a solution that makes your skin extremely sensitive to light is applied to the area with AKs. You’ll sit in the office with this on your skin for about 60 to 90 minutes. Afterward, you’ll be treated with either a blue or red light,” that “for 48 hours after treatment, you’ll need to avoid the outdoors during daylight. The UV light, even on a cloudy or snowy day, can cause a serious skin reaction,” and that “most patients with AKs need 2 PDT treatments, with the second treatment given 3 weeks after the first.” https://www.aad.org/public/diseases/skin-cancer/actinic-keratosis-treatment · Medical Organization
2. American Academy of Dermatology Association. “Actinic keratosis: Overview.” Describes an actinic keratosis as “a precancerous skin growth caused by the sun or indoor tanning,” states that “more than 40 million Americans develop actinic keratoses each year,” and that “some AKs and actinic cheilitis turn into a type of skin cancer called squamous cell carcinoma.” https://www.aad.org/public/diseases/skin-cancer/actinic-keratosis-overview · Medical Organization
3. American Academy of Dermatology Association. “How to select a sunscreen.” Broad spectrum, SPF 30 or higher, water resistant. https://www.aad.org/public/everyday-care/sun-protection/shade-clothing-sunscreen/how-to-select-sunscreen · Medical Organization
Content on this page is for educational purposes and is not a substitute for professional medical advice. Redness, swelling, stinging during treatment, and peeling across the treated area for several days are expected. Treated skin is highly sensitive to light for approximately 48 hours after treatment and must be kept out of daylight during that period. Blistering, infection, and temporary lightening or darkening of the skin are uncommon but possible. Tell us about any medication that makes your skin sensitive to light. This treatment is not suitable during pregnancy or where there is a known sensitivity to the medication used. Individual results may vary.