Reproducibility of a non-invasive skin irritancy test in a cohort of metalworker trainees

Fruit acids and sodium hydroxide in the food industry and their combined effect with sodium lauryl sulphate: controlled in vivo tandem irritation study

BACKGROUND

Cutaneous exposure to a variety of irritants has been extensively studied in recent years. Nevertheless, knowledge of the induction of irritant dermatitis, especially by mild irritants at low doses and for a short duration of exposure, is still incomplete.

OBJECTIVES

To quantify the irritant effects and barrier disruption properties of ascorbic acid (ASC), acetic acid (ACA) and sodium hydroxide (NaOH), particularly in combination with an anionic detergent, sodium lauryl sulphate (SLS).

METHODS

In a tandem repeated irritation test, the irritants were applied for 30 min twice daily for 4 days to the skin of the mid-back of 19 healthy volunteers of both sexes. We used bioengineering techniques for measurement of transepidermal water loss (TEWL) and skin colour reflectance, as well as visual scoring.

RESULTS

Repeated application of ASC and ACA caused a moderate increase in TEWL and erythema. The sequential application of ASC or ACA and SLS enhanced these effects. NaOH induced a strong reaction when applied both occlusively and nonocclusively as well as in combination with SLS, with an early onset of the inflammatory signs, leading to discontinuation of the application on the third day in most of the test fields. Notably, the irritant effect of NaOH was not as marked when applied sequentially with SLS.

CONCLUSIONS

Our results demonstrate that concurrent application of an anionic detergent and a mild acidic irritant can lead to disruption of the barrier function which, although not additive, is still considerable. The combined application of SLS and mild acids does not prevent SLS-induced irritation. Furthermore, we showed that NaOH in low concentrations may also act as a potent irritant but that its effect is not enhanced by SLS. The necessity of adequate skin protection and reduction of contact with substances that are potentially barrier disruptive and irritant, e.g. in the food industry, is emphasized, not only when handling detergents, but also when processing food products.

Modulation of irritation-induced increase of E-selectin mRNA in vivo by topically applied corticosteroids

There is a continuous need for methods to evaluate the biologic effects of topically applied drugs in the skin. Irritation of the epidermis with sodium dodecyl sulfate leads to an upregulation of E-selectin on endothelial cells and E-selectin mRNA can be detected in vivo within a short time. This study was aimed to investigate whether this biologic response can be used as a read-out for the anti-inflammatory effect of topically administered corticosteroids. We investigated skin of healthy volunteers treated according to the two following experimental protocols: (i) topical application of different corticosteroids (versus basic ointments as controls) for 12 h and irritation with sodium dodecyl sulfate 1% for 4 h; (ii) irritation with sodium dodecyl sulfate 1% for 12 h and application of the corticosteroids for 5 h. The biopsy specimens were subjected to RNA extraction and reverse transcription and competitive reverse transcriptase-polymerase chain reaction was performed using defined concentrations of a pre-constructed mimic DNA. As result, we found strong positive signals for wild-type E-selectin mRNA in all biopsies pretreated with basic ointments, whereas in biopsies from areas pretreated with corticosteroids the bands for wild-type E-selectin DNA could be detected at 10-1000 lower levels of mimic DNA concentrations. The reverse experiment, application of corticosteroids after the irritation, again yielded significantly reduced signals for E-selectin mRNA. In both experimental settings, the different strength of the topical corticosteroids used was reflected by significant differences in the amount of E-selectin mRNA found in the biopsies. This study demonstrates the pharmacologic effect of topical corticosteroids on the irritation-induced E-selectin mRNA expression on dermal endothelial cells in vivo using very small tissue samples and this approach may be of value for further pharmaceutical studies.