Why SPF Is the Most Important Step in Any Skincare Routine
Educational purposes only. This article does not constitute medical advice and is not a substitute for professional clinical consultation. Consult a qualified practitioner before making any decisions about your health or treatment.
Why does UV matter?
Ultraviolet radiation from the sun is one of the most well-studied environmental contributors to changes in skin over time. It is associated with photoageing — the alterations in skin texture, pigmentation, and structure that occur with cumulative sun exposure — as well as with more serious dermatological concerns.
This does not mean sun exposure has no benefits. Sunlight plays a role in vitamin D synthesis and has documented effects on mood and circadian regulation. The goal of photoprotection is not to avoid light entirely, but to manage exposure in a way that reduces cumulative UV damage.
What does SPF actually measure?
SPF (Sun Protection Factor) is a measure of how much UVB radiation a product filters relative to unprotected skin. SPF 30 filters approximately 97% of UVB; SPF 50 filters approximately 98%. These differences are smaller than product marketing often implies, and no sunscreen filters 100%.
UVA radiation — which penetrates more deeply and is associated with photoageing — is not fully captured by the SPF figure. For broad-spectrum protection, look for products that include UVA protection indicators alongside the SPF rating.
Why every day?
UV exposure is not limited to sunny days or summer months. UVA in particular penetrates cloud cover and glass. Cumulative exposure — the accumulation of small amounts day after day, year after year — is significant even in the absence of obvious sunburn.
Daily use, applied as the last step in a morning skincare routine and before any makeup, is the consistent recommendation from dermatological bodies.
How much to apply
Studies consistently suggest that most people apply significantly less sunscreen than the amount used in efficacy testing. The general guidance is approximately one teaspoon (around 2 mg per cm²) for the face and neck, though specific recommendations vary. Reapplication after prolonged outdoor exposure is also important.
What to look for
Look for broad-spectrum protection (covering both UVA and UVB), an SPF of at least 30 for daily use, and formulations that suit your skin type and are comfortable enough that you will actually apply them consistently. The best sunscreen is the one you will use every morning.
About the author
Dr. Elnaz Mirtaheri
Medical doctor and aesthetic medicine practitioner. Dr. Elnaz Mirtaheri takes a consultation-led, evidence-informed approach to aesthetic care — prioritising individual assessment, natural outcomes, and clinical integrity in every treatment decision.
