Photosensitivity: the 9-year experience at a Sydney contact dermatitis clinic

Keratinocytes of the Upper Epidermis and Isthmus of Hair Follicles Express Hemoglobin mRNA and Protein

The epidermis, the keratinized stratified squamous epithelium surrounding the body surface, offers a valuable framework to investigate how terrestrial animals overcome environmental stresses. However, the mechanisms underlying epidermal barrier function remain nebulous. In this study, we examined genes highly expressed in the human and mouse upper epidermis, the outer frontier that induces various barrier-related genes. Transcriptome analysis revealed that the messenger RNA level of hemoglobin α (HBA), an oxygen carrier in erythroid cells, was enriched in the upper epidermis compared with that in the whole epidermis. Immunostaining analysis confirmed HBA protein expression in human and mouse keratinocytes (KCs) of the stratum spinosum and stratum granulosum. HBA was also expressed in hair follicle KCs in the isthmus region; its expression levels were more prominent than those in interfollicular KCs. HBA expression was not observed in noncutaneous keratinized stratified squamous epithelia of mice, for example, the vagina, esophagus, and forestomach. HBA expression was upregulated in human epidermal KC cultures after UV irradiation, a major cause of skin-specific oxidative stress. Furthermore, HBA knockdown increased UV-induced production of ROS in primary KCs. Our findings suggest that epidermal HBA expression is induced by oxidative stress and acts as an antioxidant, contributing to skin barrier function.

A 20-year analysis of previous and emerging allergens that elicit photoallergic contact dermatitis

BACKGROUND

Retrospective chart reviews are periodically needed to update allergen series to detect changes in photoallergic contact dermatitis (PACD) over time.

OBJECTIVE

We sought to evaluate photopatch test results during a 13-year period and extend the observations to 20 years.

METHODS

A retrospective chart review was conducted in patients who were photopatch tested.

RESULTS

In all, 76 patients were evaluated. A total of 69 positive photopatch and 45 positive patch test reactions were detected in 30 and 23 patients, respectively. The frequencies of the positive photopatch test reactions were sunscreens 23.2%, antimicrobial agents 23.2%, medications 20.3%, fragrances 13%, plants and plant derivatives 11.6%, and pesticides 8.7%. Of the positive photopatch reactions to antimicrobial agents, 60% were caused by Fentichlor.

LIMITATIONS

This study was a retrospective chart analysis, and the number of patients was small.

CONCLUSIONS

Sunscreens and antimicrobial agents were the most frequent allergens eliciting PACD, and there was a decrease in PACD caused by fragrances. The number of reactions to medications increased. This study also demonstrated that pesticides can be a cause of PACD. The detection of reactions to Fentichlor was unexpected and, although they have been attributed in some studies to cross-reactions to sulfanilamides and bithionol, such a robust association was not observed in this study. This study extends our experience of the changes in the allergens that elicit PACD to 20 years.

Photopatch testing of 1155 patients: results of the U.K. multicentre photopatch study group

BACKGROUND

Photoallergic contact dermatitis can be difficult to diagnose if not appropriately investigated. Currently, the most common U.K. photoallergens appear to be sunscreen chemicals. The investigation of choice is photopatch testing (PPT), which is probably underused. In part, this is due to differences in methodology and results interpretation.

OBJECTIVES

To conduct PPT using a group of sunscreen chemicals, defined indications and a standardized methodology including interpretation and relevance of reactions in patients attending for investigation at 17 centres across the U.K., Ireland and the Netherlands.

METHODS

Patients (n = 1155) who fulfilled the inclusion criteria were investigated with PPT using sunscreen chemicals in addition to suspected topical products. Readings were taken at 24, 48 and 72 h following standardized ultraviolet A irradiation (5 J cm(-2)). The clinical relevance of any reaction was recorded.

RESULTS

Of the 1155, 130 had allergic reactions (11.3%). Of these, 51 had photoallergy (PA) (4.4%), 64 had contact allergy (CA) (5.5%), and 15 patients had combined PA and CA (1.3%). Multiple PA was seen in some. The most common photoallergen was benzophenone-3 (27 reactions; 21%). Most reactions (60%) were clinically relevant. The most common indication for testing in patients found to have PA was a history of reacting to a sunscreen (41%). The other 59% had an exposed-site dermatitis/skin problem or a photodermatosis. Some centres (n = 8) performed readings after the standard 48-h reading, and an extra 32 PA and 22 CA reactions were detected, which were not evident at 48 h. A new photoallergen (octyl triazone) was detected in two patients.

CONCLUSIONS

Sunscreen PA and CA are probably equally uncommon. Most reactions, of both reaction types, were relevant clinically. A large proportion of patients (59%) found to have PA was unaware of reacting to a sunscreen chemical, suggesting that PA should be considered as an explanation in any exposed-site dermatitis. Although this study focused on reactions at 48 h postirradiation, readings performed up to 96 h, while inconvenient, add value by detecting additional relevant responses. A previously unknown photoallergen was found, highlighting the need for awareness of novel photoallergens in the marketplace. A standardized PPT method not only encourages more use of this investigation, but also facilitates comparison of results between centres and so will improve our understanding of PA.