SPF, UVA and UVB
SPF describes protection against UVB radiation, a major cause of sunburn. It is not a number of hours you can safely spend in the sun. Look for broad-spectrum protection against UVA and UVB. The American Academy of Dermatology recommends a water-resistant sunscreen with SPF 30 or higher for outdoor exposure. No sunscreen blocks all ultraviolet radiation.
Application and reapplication
Cover exposed skin, including the ears, neck, feet and thinning scalp. Follow the label and apply before going outdoors. A thin or uneven layer gives less protection than expected. Reapply approximately every two hours outdoors and after swimming, sweating or towel drying, following the product instructions. Water resistance does not mean all-day protection.
Choose a tolerable formula
For acne-prone skin, a non-comedogenic formulation may be useful. A cream can be more comfortable on dry skin. Burning is not a sign that a product is working. If repeated irritation makes sunscreen difficult to use, discuss alternatives at a consultation. Makeup with SPF should not automatically replace a separate sunscreen.
Protection beyond the bottle
Use shade, a broad-brimmed hat, protective clothing and sunglasses. Reflected sunlight near water and sand still matters. Avoid tanning beds. Sun protection does not replace assessment of a changing, bleeding or unusual skin lesion. A dated photograph can help track a change but cannot establish a diagnosis.
