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Skin analysis in the acne consultation, what the UV capture actually shows

Porphyrins, pore counts and longitudinal documentation during isotretinoin therapy. We walk through the typical acne report workflow: what a 3D skin analysis shows, what it does not, and where the limits for diagnosis and advertising sit.

Updated 23 May 2026 · 7 min read

Acne is one of the most common indications for skin analysis in the dermatology consultation. Patients often arrive after long stretches of topical therapy and want to see whether the consultation brings something substantively new. The 3D skin analysis in UV mode provides three building blocks: porphyrins as a bacterial indicator, quantified pore classification and surface mapping. What it does not provide is just as important.

What the UV capture shows: porphyrins as a bacterial marker

Propionibacterium acnes (now also Cutibacterium acnes) in the sebaceous follicle produces porphyrins as a metabolic by-product. These porphyrins fluoresce under 365 nm UV light in the red spectrum at 580 to 680 nm. On the UV capture they appear as brighter spots over follicles. Increased porphyrin density in the T-zone and nasolabial region correlates with increased bacterial activity but is not a diagnosis substitute: the correlation between porphyrin signal and clinical acne severity is not 1:1 because other factors (sebum secretion, follicle blockage, inflammatory response) shape the picture.

Practice use: the UV capture is a good conversation starter. Patients see the distribution of bacterial activity on their own skin, which makes abstract recommendations on care routine, BPO application or antibiotics more plausible. It is not diagnostic proof, it is visualisation.

What the polarised captures show: pores and surface

Cross-polarised capture reduces surface gloss and reveals depth structure. The algorithm counts pores in three size classes (large, medium, small) and maps them onto anatomical regions. In acne patients with a comedonal focus you see increased counts in the T-zone, often accompanied by a hyperkeratotic surface too fine for the naked eye in the standard RGB capture.

Parallel-polarised capture shows the opposite: light reflection. This is the view in which inflammatory acne lesions (papules, pustules) visually dominate. Practices often use this capture in the first conversation because it matches the patient's self-perception.

What the skin analysis does not show

Three important diagnostic areas remain reserved for clinical history and inspection, the device does not help here:

  • Hormonal triggers: PCOS, androgen profile, cycle correlation. These are clarified by history and laboratory, not by imaging.
  • Acne inversa (hidradenitis suppurativa): The typical locations in axilla, groin, submammary are not captured by a facial skin analysis. The indication needs its own clinical examination.
  • Scar depth and type: Boxcar, icepick and rolling scars differ morphologically. 3D topography shows the height profile, but histology and depth resolution are limited by micrometre-level modelling (see manufacturer specs in our device-comparison article).
  • Differential diagnosis rosacea papulopustulosa: Optically similar, clinically different, differentiated through erythema distribution and telangiectasia patterns, not through porphyrin signal.

Longitudinal documentation during systemic acne therapy

Isotretinoin is standard for moderate to severe acne not adequately responsive to topical therapy and systemic antibiotics. Typical dose 0.5 mg/kg body weight per day with individual escalation up to 1.0 mg/kg per day. During therapy the skin is UV-sensitive, sun protection is mandatory. Source: red-hand letter and product information.

The skin analysis contributes to longitudinal documentation in three points: first, porphyrin density across therapy months (with effective isotretinoin treatment, a reduction is expected as sebum activity drops and bacterial population decreases). Second, pore counts in the T-zone. Third, during longer treatment, the skin-texture mapping as an indicator for scar formation.

Important: the data belongs in the patient record and in the consultation, not in public advertising. Before/after images for acne therapies fall under the advertising prohibition of § 11 HWG, and since the BGH ruling of 31.07.2025 (case I ZR 170/24) this also applies to minimally invasive procedures. Documentation in the record remains permitted.

IGeL or statutory insurance?

The skin analysis itself is not in the German EBM catalogue, it is an individual health service. For privately insured patients you bill via GOÄ A612 (2.3× multiplier with medical indication). For statutory-insured patients the skin analysis is an IGeL service with written information and patient consent. Details in our GOÄ article.

Practice setup for the acne consultation

We recommend the following first-consultation flow. History and clinical inspection first, without the device, because acne severity assessment (mild, moderate, severe) is clinical. Then skin analysis as additional report documentation, about 5 minutes. In the report conversation, explain the UV capture first (porphyrin distribution), then pore classification, then the planned therapy. Patients receive the link to their own report by email, with the values for later progression comparison.

Sources and further reading

As of May 2026. This article is professional information for medical and aesthetic practices, not medical advice for patients. Therapy decisions rest on your own history-taking, inspection and diagnostics.

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