Publications

Far-ultraviolet-C (far-UVC) light is increasingly being considered for infection control in public and healthcare settings because it effectively inactivates bacteria and viruses while posing minimal risk to healthy skin and eyes.  However, its safety in people with photosensitivity disorders has been uncertain.  This study, conducted at the Scottish Photobiology Service at Ninewells Hospital, integrated far-UVC phototesting into routine clinical assessment for patients with and without abnormal photosensitivity.  Eighty-three individuals were exposed to filtered far-UVC light at doses up to the current UK daily exposure limit, with careful monitoring for any skin reactions.  Despite many participants showing marked sensitivity to other ultraviolet wavelengths, none developed visible skin changes following far-UVC exposure.  These findings suggest that, within established safety guidelines, far-UVC is unlikely to pose a risk to patients with photosensitivity disorders, supporting its safe use as a germicidal technology in public spaces.

Publication:  Far-ultraviolet-C exposure in patients with photosensitivity disorders

This study investigated the effectiveness of far-UVC light (222nm) in reducing airborne microorganisms in indoor environments using a full room-scale experimental chamber.  Researchers tested filtered krypton-chloride lamps against two hospital-relevant bacteria, Staphyococcus aureus and Pseudomonas aeruginosa, under a range of mechanical ventilation rates.  The results showed substantial reductions in airborne microbial concentrations, with average inactivation exceeding 90% in most scenarios and remaining effective across different ventilation regimes, particularly at lower air change rates.  Although reduced effectiveness was observed at very short distances from the microbial source, far-UVC still achieved significant inactivation.  Overall, the findings demonstrate that far-UVC irradiation has strong potential as a supplementary infection-control technology in indoor and healthcare settings and support further investigation in real-world environments.

Publication:  Experimental analysis to quantify inactivation of microorganisms by far-UVC irradiation in indoor environments

This observational cohort study investigated whether cord blood porphyrin analysis can help identify neonates at risk of erythropoietic protoporphyria (EPP) or X-linked erythropoietic protoporphyria (XLEPP), particularly to guide safe management if neonatal jaundice requires phototherapy.  The authors derived a cord blood-specific reference interval for total erythrocyte porphyrin (TEP) of 1.2-3.1 umol/L red blood cells, which is higher than adult reference ranges, and retrospectively reviewed cord blood testing performed in UK porphyria centres between 2001 and 2024.  Of seven infants with clinical follow-up, those with normal or borderline TEP at birth did not develop photosensitivity, while markedly elevated TEP levels identified neonates with recessive EPP and XLEPP, both of whom showed increasing porphyrin levels over time.  One infant with modest TEP elevation was found to be a carrier only and remained asymptomatic.  Overall, the study shows that cord blood porphyrin analysis, particularly when distinguishing metal-free from zinc-chelated protoporphyrin, can help identify newborns at risk of painful phototoxic reactions if exposed to broad-spectrum phototherapy, but it should not be used as a definitive diagnostic test for protoporphyria at birth.

Publication:  Cord blood porphyrin analysis in neonates at risk of inheriting protoporphyria:  An observational cohort study

Photosensitivity disorders encompass a diverse group of conditions in which abnormal skin reactions occur in response to ultraviolet radiation or visible light, ranging from common entities such as polymorphic light eruption to rare and severe genetic or metabolic diseases.  These conditions may present with immediate, intermediate, or delayed reactions after light exposure and can be immunological, drug-induced, genetic, metabolic, or photoaggravated in nature.  They often have a substantial psychosocial and quality of life impact, necessitating careful clinical assessment and specialist investigation, particularly through photodiagnostic testing such as monochromator phototesting and minimal erythema dose determination.  Management is largely supportive and preventative, centred on rigorous photoprotection, patient education, and lifestyle modification, with selected use of photohardening, phototherapy, systemic immunomodulatory treatments, and targeted therapies depending on the underlying diagnosis.  Despite advances in diagnostic techniques and emerging therapies, photosensitivity disorders remain under-recognised and underserved, highlighting the need for improved access to specialist services, earlier diagnosis, and ongoing research to optimise care and patient outcomes.

Publication:  Clinical Perspectives on Photosensitivity and Photodiagnostics

This UK multicentre cross-sectional study characterised the clinical and photobiological features of solar urticaria (SU), a rare immune-mediated photosensitivity disorder, in 178 phototest-positive patients recruited from six tertiary photobiology centres between 2019 ad 2023.  The majority of patients were female, with a median disease onset age of 35 years, and SU was observed across all ethnicities and skin phototypes, although lighter phototypes were most common.  UVA radiation was the most frequent triggering waveband, either alone or in combination with visible light or UVB, with some variation between skin phototypes.  Most patients had co-existing atopic disease, and while almost all used sunscreen and antihistamines, complete disease control was uncommon.  Omalizumab provided the highest rate of complete symptom control compared with other treatments, highlighting its importance despite being an unlicensed indication.  Overall, the findings demonstrate the clinical heterogeneity of SU and the ongoing need for more effective, standardised treatment strategies. 

Publication:  Characterization of the clinical and photobiological features of solar urticaria:  A UK multicentre cross-sectional study

This study evaluates how well different types of eyewear protect the eyes from ultraviolet (UV) radiation in patients undergoing PUVA photochemotherapy after taking oral psoralen, a drug that increases sensitivity to UV light for 12-24 hours and raises the risk of eye damage.  A range of glasses, including sunglasses, prescription lenses, and specialised UV-protective eyewear, were tested using laboratory and simulated real-world conditions  While most lenses blocked UV radiation effectively in controlled measurements, the study found that overall protection in practice depends heavily on frame design, fit, and coverage, as gaps around the eyes can allow significant UV exposure from indirect or angled light.  Wrap-around, close-fitting glasses with larger lenses and darker frames provided the best protection, whereas poorly fitting or narrow-framed styles allowed greater UV leakage.  The findings highlight that lens transmission alone is not a reliable indicator of eye safety and emphasis e the importance of well-designed, properly fitted eyewear to minimise ocular risk during the photosensitivity period following PUVA treatment.

Publication: An investigation into eye protection for patients receiving oral psoralen photochemotherapy (PUVA)

This letter describes Scottish experience with afamelanotide for managing cutaneous phototoxicity in erythropoietic protoporphyria (EPP), a rare genetic condition causing severe, painful reactions to sunlight that markedly impair quality of life.  Afamelanotide, an a-melanocyte-stimulating hormone analogue, increases protective eumelanin and is the only approved preventive treatment for adult EPP, though not yet licensed in the UK.  Through Scotland's ultra-orphan medicines pathway, 13 adults received the treatment between 2022 and 2024, with outcomes audited in 10 patients treated in NHS Tayside.  Treatment resulted in significant improvements in both time to symptom onset when exposed to light (median increase from 10 to 120 minutes) and quality of life (median improvement of 7.5 points on a 0-10 visual analogue scale), with all patients choosing to continue therapy.  Despite logistical challenges, including sourcing implantation devices, the authors report an overall positive experience and note that afamelanotide use in Scotland has been extended to allow further data collection.

Publication: Afamelanotide in managing cutaneous phototoxicity in erythropoietic protoporphyria: a Scottish perspective

The study reviewed minimal erythema dose (MED) test results from over 1,000 patients across phototherapy centres in Dundee and London to better understand how skin types respond to narrowband UVB light before treatment.  MED values generally increased with darker Fitzpatrick skin phototypes, but there was substantial overlap between groups and between centres, with Dundee showing slightly lower MEDs than London.  Non response to testing was very rare among lighter skin types (I-III) but more common in darker skin types (IV-VI), suggesting that broader or higher test dose ranges may be needed for these patients.  Overall, the findings support the current testing approach for lighter skin types and highlight the need for adjusted protocols to ensure accurate, inclusive, and safe phototherapy dosing across all skin types.

Publication: Narrowband ultraviolet B minimal erythema dose reference range  

Broad-spectrum abnormal localized photosensitivity syndrome (BALPS) is a rare condition in which sunlight triggers recurrent, itchy red rashes at the same specific skin sites.  This case report describes a man with a 10-year history of sun-induced eruptions confined to the waistline and underarm areas.  Specialized phototesting showed abnormal sensitivity to both UV-A and UV-B light only in the affected skin, while unaffected areas responded normally.  These findings helped confirm the diagnosis and distinguish BALPS from more widespread photodermatoses.  Management focuses on strict photoprotection of the affected areas and topical corticosteroids during flare-ups.  Increased awareness of BALPS is important to support accurate diagnosis and improve patient outcomes.

Publication: Broad-Spectrum Abnormal Localized Photosensitivity Syndrome

Photodiagnostic testing is a vital tool for diagnosing conditions where the skin is abnormally sensitive to light. Historically, comparing how much ultraviolet (UV) radiation triggers a reaction has been difficult because different light sources and wavelengths produce widely different results when measured in traditional units (mJcm−2). To solve this, we can use the Standard Erythema Dose (SED), a measurement designed to be independent of the specific light source used. Using SED significantly reduces the variation between different wavelengths, allowing doctors to more consistently compare phototesting results with established "normal" ranges regardless of the equipment or the specific centre performing the test. This standardisation leads to more reliable and accurate diagnoses for patients with photosensitivity.

Publication: Quantity of ultraviolet radiation required to produce erythema: normal ranges in phototesting