After laser, chemical peel, or pigmentation treatments, your skin becomes sensitive to irritation and UV rays, so thorough sun protection is essential for recovery and maintaining results. Among UV rays, UVB causes sunburn, while UVA, which penetrates deeper, causes photoaging and is also linked to hyperpigmentation; therefore, broad-spectrum products that block both UVA and UVB are recommended. SPF is primarily an indicator of UVB protection; SPF 15 blocks about 94%, SPF 30 about 97%, and SPF 50+ about 98% of UVB rays. For an adult’s entire body, apply approximately 35 mL (about 7 teaspoons) 20–30 minutes before sun exposure, and reapply every 2 hours or after sweating or swimming. Consistent, broad-spectrum protection also helps prevent wrinkles, age spots, and hyperpigmentation. Sun protection is especially important after pigmentation or melasma treatments, as re-exposure to UV rays can cause pigmentation to return. Specific post-treatment care guidelines vary depending on the type of procedure and skin condition, so please consult your doctor for details. This information is for reference only and does not constitute a diagnosis. Please consult a specialist before undergoing any actual procedure.
[Source] https://dermnetnz.org/topics/topical-sunscreen-agents