SPF
Also written as: SPF — Sun Protection Factor
Sun Protection Factor; a numerical measure of a sunscreen's ability to protect skin from UV-B radiation, appearing on product labels and post-procedure care documentation in cosmetic dermatology.
Full Definition
SPF, or Sun Protection Factor, quantifies how much UV-B radiation a sunscreen product blocks relative to unprotected skin. An SPF 50 product blocks approximately 98% of UV-B rays. In cosmetic dermatology, SPF recommendations are ubiquitous in post-procedure instructions, particularly following laser treatments, chemical peels, and microneedling, when skin is especially photosensitive. Editors must ensure 'SPF' is followed by a space and a numeral (SPF 30, SPF 50), and should flag instances where SPF is incorrectly used to imply UV-A protection (which requires a separate PA or broad-spectrum designation). SPF should be expanded on first use in formal clinical documents.
Usage
Usage note: Always write as 'SPF [numeral]' with a space. Do not hyphenate. Expand on first use in formal documents. SPF measures UV-B only; do not conflate with broad-spectrum or UV-A protection claims.
In Context
- "All patients undergoing ablative procedures were advised to apply SPF 50 sunscreen daily for a minimum of six weeks post-treatment." — Clinical protocol
- "The editor corrected 'SPF-50' to 'SPF 50' to align with the house style guide." — Editing annotation