Procedure

Photodynamic Therapy

A light-activated drug applied in the office, then switched on with a lamp or laser. It is the strongest non-drug option for inflammatory acne, and the downtime is a real week.
Dr. Schwarz, MD · Board-certified dermatologistLast reviewed August 23, 2026
A rectangular LED panel in a white frame, angled on a white background, its face filled with a dense grid of several hundred small blue lights all lit, casting a blue glow onto the surface beneath it.

Start here

Photodynamic therapy is the strongest non-drug option for acne, and the one most likely to be sold to the wrong person — it hits the oil gland and the bacteria at once, and significant inflammatory acne can improve a lot. Two things get glossed over: in the US it is approved for precancerous sun damage, not acne, so protocols vary between clinics; and the downtime is several days of a red, swollen, peeling face with 48 hours where sunlight genuinely hurts.

I reach for it in a narrow situation: significant inflammatory acne where isotretinoin is not possible, and where the person can genuinely take a week out of view. Otherwise the trade is not worth it.

— Dr. Schwarz, Board Certified Dermatologist

Key Facts

−
Also calledPDT, ALA-PDT, Levulan, blue light with Levulan, aminolevulinic acid photodynamic therapy
Downtime2 to 7 days of redness, swelling, and peeling, plus strict light avoidance for 48 hours
Sessions2 to 3, spaced 2 to 4 weeks apart
Typical costAbout $400 to $1,500 per session in the US when done for acne; varies by location and protocol
Results timelineA flare in the first 1 to 2 weeks, then improvement over 1 to 3 months
PainStinging and burning during the light phase, usually the most uncomfortable part
Skin tone safetyCan be done on all tones, but the risk of dark patches afterward is higher on deeper skin tones

What It Is

−

A two-part treatment. First a drug makes the skin temporarily light-sensitive — usually 5-aminolevulinic acid, sold as Levulan. It sits on the skin for 20 minutes to 3 hours and is taken up mostly by oil glands and rapidly dividing cells. Then a blue or red light, sometimes a pulsed dye laser or intense pulsed light, activates it. In the US, PDT is FDA-approved for actinic keratoses — precancerous sun spots — and using it for acne is off-label, which is common and accepted but means protocols vary between clinics.

How It Works

−

The drug is converted inside cells into protoporphyrin IX, which builds up in oil glands. Light of the right color makes it release reactive oxygen that destroys the cells holding it. That damages the oil gland so it makes less sebum, and it kills Cutibacterium acnes, the bacteria involved in inflamed acne. The longer the drug sits before the light, the deeper it reaches and the stronger — and more uncomfortable — the reaction. That incubation time is the main dial a provider turns.

Skin is about two millimetres thick on the face. How deep a treatment reaches decides what it can change, and whether it treats all of the skin or scattered columns of it decides how long you take to heal.

How it works
Compare
Skin basics
EPIDERMISDERMISFAT0.05 mm — pigment0.5 mm — texture + pores1.0 mm — collagen1.5 mm — deep dermisPEELNEEDLINGNON-ABLATIVE LASERABLATIVE LASERREACHES THE UPPER DERMIS

This reaches just past the epidermis into the top of the dermis, around half a millimetre down. That is where fine texture, pores and the shallowest scarring sit. Deep enough to remodel a little, shallow enough that healing is measured in days.

A peel or a scrub takes the skin off evenly from the surface down. Everything above the line goes and nothing below it is touched, which is why peels suit surface pigment and rough texture, and why the whole face flakes for a few days after.

Needles make hundreds of separate channels and leave the skin between them untouched. That untouched skin is what heals the rest, so recovery is quick — but a needle only injures the skin to start repair. It removes nothing.

The light passes through the surface and heats a column underneath it. The surface stays whole, so you leave red rather than raw — and it takes a course of sessions rather than one.

The laser removes columns of skin outright: the white gaps here are tissue that is gone, and new skin grows in from the sides. The strongest of the four, and the longest to heal.

The outer layer, and the only one anything in a jar reaches. It renews itself constantly: a cell made at the bottom takes about a month to reach the surface and flake off. Most of what a skincare product does, it does here.

The living layer underneath, holding the blood vessels, the nerves and the collagen. It is where lasting change happens and it is hard to reach: most of what is sold for the skin never gets this far.

What It Treats

−
Actinic Keratosis
Actinic Keratosis
Strong evidence
A light-activated liquid is put on the whole area, left to soak in, then activated with a lamp. It treats a broad field in one or two clinic visits instead of weeks of cream, which suits people who cannot manage a long course at home. The area stings during treatment and is red, swollen and sore for several days, and the treated skin has to be kept out of light straight afterwards.
Basal Cell Carcinoma
Basal Cell Carcinoma
Moderate evidence
A light-sensitizing cream is left on the tumor and then activated with a lamp, usually in two sessions. It is for thin superficial tumors only, confirmed by biopsy, and it has the advantage of treating the sun-damaged skin around them at the same time. It stings during the light, and the cure rate is lower than surgery.

Not the Best For

−
Squamous Cell Carcinoma
Squamous Cell Carcinoma
Limited evidence
A light-activated cream treatment for the earliest forms only — actinic keratoses and some cases of carcinoma in situ. It treats a whole patch of sun-damaged skin at once and heals with a good cosmetic result. It has no role in an invasive tumor, and using it on one delays proper removal.
Close-up of a cheek with inflamed acne. Raised pink-red bumps, a few with yellow-white heads, sit in a patch of redness, and the skin between them is dry and flaking.
Acne
Limited evidence
Can help stubborn inflamed acne, but the protocols vary widely between clinics, the downtime is real, and the evidence is not strong enough to put it ahead of the options above.
Two skin close-ups side by side, labeled Whitehead (Closed Comedone) and Blackhead (Open Comedone)
Blackheads and whiteheads
Doesn't work
The treatment targets the oil gland and the bacteria. It does not open a pore that is already blocked.
Close-up of the cheek, nose and mouth of an adult with light skin, turned three-quarters away from the camera against a pale blue background. The surface of the cheek is uneven, dimpled with shallow depressions and small pits that catch the light. There are no active spots — the change here is in the texture of the skin rather than its color.
Acne scars and dark marks
Doesn't work
It works on acne that is active now, not on what earlier acne left behind.

Pros and Cons

−
Pros
  • Two targets at once It cuts oil production and kills acne bacteria.
  • Strong for inflammatory acne Trials in moderate to severe acne show a lot.
  • No systemic drug No pills, no blood tests, no pregnancy prevention program.
  • Few sessions Usually 2 or 3, not a long course.
Cons
  • Real downtime Days of redness and peeling, and 48 hours out of the light.
  • Painful The light phase stings and burns, and it is hard to sit through.
  • Off-label and unstandardized Drug, timing and light source differ by clinic.
  • Not permanent Acne commonly returns over 6 to 12 months.
  • Pigment risk Dark patches afterward are a genuine concern on deeper skin tones.

How to Prepare

−
2 weeks before5 to 7 days beforeOn the day
Sun and tanning
2 weeks before
Avoid sun and tanning for 2 weeks.
Actives
5 to 7 days before
Stop retinoids and exfoliating acids.
Sun protection
On the day
Bring a wide-brimmed hat, sunglasses and mineral sunscreen for the trip home, and have someone else drive if you can.
Before you book
Clear several days, especially the 48 hours after, when you must stay out of sunlight and bright indoor light.

What Happens

−
ArrivingThe treatmentLeaving
Arriving
Photos, consent covering the off-label use and the downtime, and a medication review. No numbing — cool air is used during the light phase, because the discomfort is heat and stinging that numbing cream does not reach. Your provider will ask about these things.
The treatment
Skin is cleaned and degreased, sometimes with microdermabrasion or an acetone wipe, so the drug soaks in evenly. The solution goes on and you wait 20 minutes to 3 hours in a dim room. Then eye shields go on and you sit under a blue or red light for 8 to 20 minutes, or a laser or IPL is passed over. Stinging builds and peaks at the end; cold air helps.
Leaving
The least comfortable procedure on this list. You walk out bright red, swollen and hot, and you will not want to be seen, so cover completely for the journey home. The burning eases within an hour or two, leaving a sunburned feeling for a day or more.

Recovery

−
First 48 hoursDays 4 to 10Weeks 1 to 2
First 48 hours
Stay strictly out of sunlight and bright indoor light; daylight through a window can trigger a severe reaction. Swelling peaks in the first 24 hours, often around the eyes, then falls. Skin darkens, feels tight, and can crust.
Days 4 to 10
Peeling and flaking, sometimes in sheets. Redness fades over the following week or two. Do not pull at peeling skin.
Weeks 1 to 2
An acne flare is common in the first week or two, before improvement starts.

Aftercare

−
48 hours48 to 72 hours5 to 7 days
Sun
48 hours
Absolute avoidance for 48 hours, including bright indoor light and daylight through glass. Then SPF 30 or higher and a hat for at least 4 weeks.
Exercise
48 to 72 hours
Wait 48 to 72 hours.
Makeup
5 to 7 days
Wait until peeling is complete, usually 5 to 7 days.
Actives
Restart retinoids and acids after 2 weeks, or once skin is fully healed.

Risks

−

Most of this treatment's side effects are guaranteed rather than possible, and they are set out on the recovery timeline above. What follows is what might go wrong.

Dark patches
Post-inflammatory hyperpigmentation is one of the more likely lasting problems, more common and slower to fade on deeper skin tones. Easier to treat early.
Prolonged redness
Redness still increasing after a week, or lasting beyond 4 weeks.
A cold sore outbreak
A common trigger. Antivirals work best started early.

Combining Treatments

−
Same day
Oral acne medicines
Antibiotics, spironolactone and hormonal treatment can all continue.
Same day
Pigment creams
Azelaic acid or hydroquinone are often used afterward for brown marks.
Pause each session
Topical retinoids and acids
Paused around each session and resumed after; they help hold the result.
Wait 4 weeks
Laser, peel or microneedling
At least four weeks on the same area, and only once skin has healed.
Wait 6 months
Isotretinoin
Not combined with it; most providers wait around six months after a course.

Insurance Coverage

−

Insurance does not cover PDT for acne, because the approved indication is precancerous sun damage. When PDT is done for actinic keratoses it is often covered — same machine, different goal.

Ask Your Doctor

−
If you are pregnant or breastfeeding
Ask the doctor managing your pregnancy or breastfeeding first.
If you have a photosensitivity disorder
Porphyria and related disorders. The whole mechanism is light sensitivity, so this is an absolute no.
If you are allergic to the drug used
Including aminolevulinic acid and related compounds.
If you have an infection or cold sore
Anything active in the treatment area has to be treated first.
If you finished isotretinoin recently
Most providers wait about 6 months.
If you cannot avoid light for 48 hours
If your circumstances make that impossible, this is not the treatment for you.
If you have a deeper skin tone
The strong inflammatory reaction raises the risk of dark patches lasting many months. Shorter incubation, a lower light dose, and a provider experienced in deeper skin tones all matter, and some pre-treat with a pigment cream.
If you take a sun-sensitizing medicine
Doxycycline, some diuretics, sulfa drugs and others amplify the reaction. Bring a full list.
If you have melasma
The heat and inflammation can worsen it.
If you work outdoors
The 48-hour light restriction is not negotiable, so a schedule that cannot accommodate it rules out the timing.

At-Home Versions

−
Blue light masks and LED devices
Okay alternative
Light without the photosensitizing drug, which is a fundamentally weaker treatment. Mild benefit in mild inflammatory acne, and nothing like PDT.
Red light devices
Okay alternative
Marketed for acne and inflammation, with limited supporting evidence at home-device power levels.
The photosensitizing drug
Bad alternative
It is applied under supervision for good reason. Self-applying it and going into daylight causes serious burns.

How It Compares

−
A gloved hand holding a laser handpiece against the cheek of a woman with acne as she lies on a treatment bedA white and brushed-steel laser handpiece lying horizontally on a white background, with a pale blue lens at the left-hand tip and a braided gray fiber cable running off to the right.
1726 nm laser
The same
Shrinks the same oil glands with no photosensitizing drug and no week of peeling. Three sessions, more expensive, and results build slowly instead of arriving after a hard week.
Isotretinoin
The same
The best studied option for severe acne and usually the cheaper one, at the cost of a months-long course, monitoring and strict pregnancy rules.
A small clear glass bowl holding a shallow pool of pale amber liquid on a white background, with a white fan-shaped brush lying beside it, bristles resting against the bowl.Diagram: how Chemical Peel works in the skin
Chemical peel
Different job
Far cheaper and far gentler, working on clogged pores and marks rather than on the glands. A step below in strength, and a reasonable one for milder acne.
Oral antibiotics
Different job
Faster and cheaper for inflamed acne, but time-limited. PDT is often what comes up after antibiotics have been used more than once.

Finding a Provider

+

This should be done by, or supervised by, a board-certified dermatologist. Ask which drug they use, how long the incubation is, which light source, and how many acne cases they have treated with that protocol — the answers vary widely and shape both the result and the downtime. Ask how they handle dark patches afterward. Red flags: no mention that the acne use is off-label, downtime described as "a day or two", no written light-avoidance instructions, and a photo gallery showing only one skin tone.

Questions Patients Ask

+

Is photodynamic therapy approved for acne?

Not in the US. It is FDA-approved for precancerous sun spots; using it for acne is off-label. That is legal and common, but it means no standard protocol and results that vary between clinics.

How bad is the downtime really?

Plan for 5 to 7 days of a visibly red, then swollen, then peeling face, with the worst in the first 48 hours. It is closer to a medium-depth peel than a laser facial.

Why do I have to stay out of the sun for 48 hours?

The drug is still in your skin, and sunlight — including through a car or office window — activates it and can cause a severe burn. This is the most important instruction of the treatment.

Does it cure acne?

No. Improvement typically lasts 6 to 12 months and repeat courses are often needed. It does not treat scars or existing brown marks.

Is it safe on deeper skin tones?

It can be done, but the risk of lasting dark patches is meaningfully higher, because the treatment works by causing strong inflammation. A shorter incubation, a lower light dose and an experienced provider make a large difference.

References

+