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Photodynamic Therapy for Acne: What the Trials Show

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Kelsey Hart

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Last reviewed

4 min read Every claim sourced · links checked 11 Sep 2026

Quick Summary

Photodynamic therapy sits inside the AAD’s insufficient-evidence statement on physical modalities, named specifically as PDT with aminolevulinic acid. Trials are numerous but mostly small, short, and compared against other active treatments rather than vehicle. Where vehicle controls do exist, the benefit largely disappears. The side-effect burden is real and immediate.

Blue LED light therapy panel over a face during a clinic session
Where the guideline standsInsufficient evidence to recommend either way
AvailabilityIn clinic
How long before you judge itA series of sessions
PregnancyDiscuss with your clinician.
Sources behind this page7, every one linked at the bottom
Photodynamic Therapy for Acne at a glance. Recommendation strength and evidence certainty are separate axes under GRADE.

What it is

Photodynamic therapy is a two-step procedure. A photosensitising drug is applied to the skin and left to soak in, usually 5-aminolevulinic acid (ALA) or its ester methyl aminolevulinate (MAL), for anything from twenty minutes to several hours. Both are precursors that skin cells convert into protoporphyrin IX, which accumulates preferentially in sebaceous glands and in Cutibacterium acnes. The treated area is then illuminated, usually with blue light, red light, a pulsed dye laser or intense pulsed light. The absorbed light excites the protoporphyrin and generates reactive oxygen species that damage the gland and the bacteria. The intention is a lasting reduction in sebum production, closer in ambition to isotretinoin than to a topical.

What the evidence actually shows

The guideline’s physical-modalities statement names it directly: “Available evidence is insufficient to develop a recommendation on the use of … photodynamic therapy with aminolevulinic acid for the treatment of acne.”

There is no shortage of studies. A 2024 systematic review screened 1122 records and included 82 studies covering 4340 patients, of which 25 were randomised controlled trials. Half the patients received ALA-PDT and a tenth MAL-PDT. Average follow-up after study completion was three months, ranging from two weeks to thirteen months. The authors summarised the entire body of work as showing “a partial clinical response”, and called for standardised protocols and direct comparisons against other acne treatments.

The vehicle-controlled data are less flattering. The 2016 Cochrane review found that 20% ALA-PDT activated by blue light showed little or no difference in effectiveness compared with vehicle plus blue light, and that across three trials in 360 participants, MAL-PDT activated by red light was no different from placebo cream plus red light. When the light is held constant and only the drug varies, the drug’s own contribution becomes hard to see.

Individual trials show the same pattern. In a randomised, controlled, split-face trial of 44 patients published in the Journal of Cosmetic Dermatology in 2010, ALA was applied for 60 to 90 minutes before three pulsed dye laser sessions on one side of the face. Global acne severity improved on both sides, significantly more on the treated side, but only 30% of patients were judged responders on inflammatory lesion counts, and 7% on non-inflammatory counts. A 2017 split-face study comparing ALA with red light against ALA with intense pulsed light enrolled twelve patients and had no vehicle arm at all. That is the typical size and design of this literature, and it is why enthusiasm ran ahead of the evidence.

How it is actually used

This is an in-clinic procedure, usually a short course of sessions a few weeks apart, priced per session and paid out of pocket. Aetna’s medical policy, as one example, lists blue light with topical aminolevulinic acid among treatments it considers experimental, investigational or unproven for acne. The ALA product itself is used off-label: the Levulan Kerastick label is approved for minimally to moderately thick actinic keratoses of the face, scalp or upper extremities, not for acne. Protocols vary enormously between clinics in incubation time, light source, energy and number of sessions, with no agreed standard, which is a large part of why the trial results cannot be pooled meaningfully. Plan for downtime afterwards. If a clinic quotes a course without discussing the photosensitivity period, that is a bad sign.

Safety and who should avoid it

The side-effect burden is the best-characterised thing about acne PDT. In the 2017 split-face study, pain during ALA with red light was rated 5 out of 10 on a numerical scale, against 2.5 for intense pulsed light; a third of participants had a transient acne flare, and 17% developed hyperpigmentation on the red light side. Erythema, swelling, oozing and crusting are routine. Photosensitivity is the part people underestimate: the Levulan label instructs patients to avoid sunlight and bright indoor light at the treated site for 40 hours, and states plainly that sunscreens will not protect against the reaction. Pigment change is a particular concern in darker skin. Long-term and pregnancy data are absent.

Commonly repeated: Photodynamic therapy is “isotretinoin without the pills”, a one-off way to shut sebaceous glands down for good. What the evidence actually shows: No trial has demonstrated that. The vehicle-controlled comparisons in the Cochrane review found ALA-PDT and MAL-PDT performing much like the light alone; follow-up across the published literature averages about three months; and the AAD work group concluded the evidence was insufficient to recommend it either way.

Related treatments we’ve reviewed: Laser and Light Therapy for Active Acne, Pneumatic Broadband Light for Acne.

Sources

Keep reading

See where this sits against every other acne treatment on the acne treatment evidence map, or check how it combines with another ingredient in the ingredient combination checker. For the guideline’s own wording on this, see the 2024 AAD guideline, recommendation by recommendation.

Not medical advice

This page reports what the published evidence says about a treatment. It is not a treatment plan and it cannot account for your skin, your other medications or your medical history. Nothing here has been reviewed by a clinician; see our editorial policy for what that means. Talk to a clinician before starting or stopping any prescription treatment.

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Written by

Kelsey Hart
Kelsey Hart is the pen name of the person behind TipsForAcne.com. I’m not a dermatologist and have no medical training. I’m a 30-something with adult, hormonal acne who got tired of advice that fell apart under scrutiny. The research and drafting here are AI-assisted, and nothing gets published unless it traces back to a guideline, systematic review, trial or drug label, linked on the claim so you can check it instead of trusting me. No clinician has reviewed these articles.

Why a pen name? · How I research · Report an error

Research, not medical advice. Every clinical claim above links to the guideline, systematic review, trial or drug label it came from, so you can check it yourself rather than take my word for it. It was researched and drafted with AI assistance by a non-clinician, and no dermatologist has reviewed it: this site does the reading, it doesn’t practise medicine. It can’t account for your circumstances either, so talk to a dermatologist or doctor about your own skin, especially before starting or stopping a prescription treatment.