Scapular reactivity to contact irritants: application-time and area variations

Area of Science:

• Dermatology
• Toxicology
• Cutaneous Science

Background:

• Repeated patch testing is crucial for evaluating skin irritants.
• Understanding variations in skin sensitivity is key for accurate dermatological assessments.
• Lapyrium chloride (LC) and sodium lauryl sulfate (SLS) are common chemicals with known irritant properties.

Purpose of the Study:

• To investigate the influence of application time and anatomical site on cutaneous reactivity to lapyrium chloride (LC) and sodium lauryl sulfate (SLS).
• To determine if skin sensitivity to these chemicals varies diurnally and regionally on the scapula.

Main Methods:

• Twenty-two male volunteers underwent 5-day repeated patch testing with varying concentrations of LC and SLS.
• Patches were applied to different scapular sites (paravertebral, lateral, medial) at randomized times (08:00, 16:00, 00:00) for 6 hours.
• Skin reactions were scored using a 13-point scale at 2, 10, and 18 hours post-patch removal.

Main Results:

• Cutaneous reactivity to LC and SLS showed statistically significant variations based on application time and body area.
• LC responses were highest at 16:00 and lowest at 00:00 on most days.
• SLS reactivity differences were significant on day 2, with highest scores at 00:00 and lowest at 16:00.
• Strongest reactions to LC were in the scapular center, while SLS reactions were strongest paravertebrally on day 2.

Conclusions:

• Diurnal variations and regional differences significantly impact skin's response to chemical irritants like LC and SLS.
• Application timing and specific skin sites must be considered in patch testing protocols for accurate irritation assessment.
• These findings highlight the dynamic nature of cutaneous sensitivity and its implications for dermatological testing and product safety evaluations.