Sunscreen use optimized by two consecutive applications.

Area of Science:

• Dermatology
• Photoprotection

Background:

• Sunscreen application is crucial for preventing sunburn.
• Inadequate application often leads to insufficient photoprotection.

Purpose of the Study:

• To evaluate the impact of two consecutive sunscreen applications on sunscreen quantity and missed skin areas compared to a single application.
• To quantify the increase in sunscreen applied and the reduction in unprotected skin areas.

Main Methods:

• Thirty-one volunteers applied sunscreen twice consecutively in a controlled laboratory setting.
• Black light photography was used to assess sunscreen coverage, correlating darkness with quantity.
• Quantification of sunscreen applied and percentage of missed skin area was performed after each application.

Main Results:

• A single sunscreen application left a median of 20% of body surface missed.
• Double application significantly reduced the missed area to a median of 9%.
• The quantity of sunscreen applied increased by 13%–100% with a second application.

Conclusions:

• Double sunscreen application substantially enhances coverage and quantity applied.
• This method significantly reduces the percentage of missed skin areas.
• Recommending double application is advised for improved sunburn protection, particularly before intense sun exposure.