Should We Use Sunscreen 365 Days a Year? SPF Guide
"80% of sun damage comes from daily incidental exposure — not from a few hours spent at the beach. That's why sunscreen should be a part of your morning routine, not just your summer routine."
– Pharm. Berfin Işık, Pharmacist and Skincare Expert
Sunscreen is the most fundamental skincare product, protecting the skin against UVA and UVB rays and providing daily photoprotection. Accepted by dermatologists as the most effective and proven method of protection against aging, sunscreen should be used not only at the beach but every season and every day. So, what is UV radiation, how does it damage the skin, and how should one choose the right sunscreen? In this comprehensive guide, we will break down the scientifically-backed information step by step.
Why Should You Use Sunscreen 365 Days a Year?
Sun protection is essential not only in summer but also in winter. UV rays reach your skin even on cloudy days, and even in fog and rain. Research shows that 80% of sun damage comes from daily incidental exposure. Hours spent by a window in the office or walking on the street, not just a few hours at the beach, can lead to serious skin damage from UV exposure.
Although UV intensity is lower in winter months, it still poses a significant threat to anyone spending time outdoors. In addition, the reflective property of snow surfaces can multiply the UV effect — white surfaces reflect sunlight, exposing your skin to UV radiation twice. When makeup, frequent cleansing, incorrect product use, and certain invasive procedures weaken the skin's protective barrier, the risk of UV damage increases even further.
What is UV Radiation? (UVA vs. UVB Differences)
Sun rays are a type of electromagnetic radiation that reaches Earth's atmosphere. UV (ultraviolet) rays are invisible rays with wavelengths between 100–400 nm. These rays are divided into two main types:
- UVB (280–320 nm): Absorbs energy in the surface layer of the skin (epidermis). It forms thymine dimers in DNA, causing sunburn, DNA damage, and cell death. UVB is the primary cause of nonmelanoma skin cancers and directly triggers DNA strand breaks.
- UVA (320–400 nm): Penetrates deeper and forms reactive oxygen species (ROS) that break down collagen and elastin fibers in the dermis. UVA increases the risk of premature aging, spots, and melanoma. Although it indirectly damages DNA, its effects are more destructive in the long term.
Simply put: UVB causes short-term damage by burning the skin's surface; UVA penetrates deep into the skin, increasing the risk of aging and cancer. Both are harmful, and effective sunscreen should provide protection against both types of radiation.
Effects of Sun Damage on the Skin
| Effect | Description |
|---|---|
| Photoaging (Premature Aging) | UVA rays activate matrix metalloproteinase (MMP) enzymes, which break down collagen and elastin. Skin elasticity decreases, and fine lines and wrinkles appear. Photoaging can progress much faster than chronological aging. |
| Hyperpigmentation (Spots) |
UV damage stimulates melanocyte cells to produce excessive melanin. Dark spots on freckles, sun spots (solar lentigo), and post-inflammatory hyperpigmentation occur. |
| DNA Damage and Cancer Risk | UVB forms thymine dimers in the skin's DNA. If the cell's repair mechanisms are insufficient, it leads to mutation and the risk of melanoma and basal cell cancer. UVA also indirectly damages DNA through free radicals. |
| Collagen Degradation and Wrinkles | Proteinase enzymes break down the structural proteins of the dermis. Skin health and elasticity are lost, wrinkles deepen, and skin thickness decreases. |
| Increased TEWL and Dryness | UV damage weakens the stratum corneum and dermoepidermal barrier. Water loss (TEWL) increases, skin dryness worsens, and irritation occurs, especially in sensitive skin. |
| Chronic Inflammation | Chronic UV exposure perpetuates skin inflammation. Symptoms like rosacea, acne, and eczema worsen, and cytokine production increases, accelerating aging. |
What Do SPF, PA, and Broad Spectrum Mean?
SPF (Sun Protection Factor): Indicates the level of protection against UVB radiation. SPF 30 provides 30 times more protection compared to the time it takes for your unprotected skin to get sunburned. However, this is not an absolute time — it depends on skin type, UV index, sun intensity, correct application amount, and reapplication frequency. According to the FDA, an SPF of 15 or higher is recommended.
PA (Protection Grade of UVA): Indicates the level of UVA radiation blockage. Graded according to the Japanese standard:
- PA+: ~1/4 of UVA is filtered (minimal protection)
- PA++: ~1/2 of UVA is filtered (moderate protection)
- PA+++: ~3/4 of UVA is filtered (high protection)
- PA++++: More than 90% of UVA is filtered (maximal protection)
Broad Spectrum: Refers to products that provide protection against both UVB and UVA. Research has shown that a product lacking a UVB filter provides immunosuppression, while a broad-spectrum product with the same SPF provides significantly more protection.
Recommended Choice: For daily use, SPF 30–50; for outdoor activities or the beach, SPF 50+. UVA protection should always be at PA++ or PA+++ level, preferably broad-spectrum products.
Chemical vs. Physical Filter Comparison
| Feature | Chemical Filter | Physical (Mineral) Filter |
|---|---|---|
| Mechanism of Action | Absorbs UV rays, converts to heat | Reflects and scatters UV rays |
| Onset of Action | 15–20 minutes (needs to be absorbed into the skin) | Immediate (protection starts after application) |
| Texture and Appearance | Light, homogeneous, "invisible" layer on the skin | Thicker, may leave a white cast |
| Skin Penetration | Yes, can penetrate the dermis (systemic absorption) | No, stays on the skin's surface (minimal absorption) |
| Irritation Risk | May cause irritation in sensitive skin (avobenzone, octinoxate) | Generally well-tolerated, hypoallergenic |
| Water Resistance | Variable (depends on formulation) | Generally more resistant |
|
Ingredients |
New and old generation chemical filters | Titanium dioxide, zinc oxide |
| Suitable Skin Types | Normal, oily, combination skin | All skin types, especially sensitive, reactive, rosacea, eczema, children, pregnant women |
| Price | Generally more affordable | More expensive |
| Advantages | Light texture, homogeneous appearance, low comedogenic score | Immediately effective, stable formulation, minimal systemic absorption, hypoallergenic, safe profile |
| Disadvantages | Potential irritation, systemic absorption | Leaves white cast, thicker texture, heavy feel |
Hybrid Formulas (Combination): Products containing both chemical and physical filters provide broad-spectrum protection while having a lighter texture. They are an ideal choice for most skin types — offering superior technology and tolerance together.
How to Choose the Right Sunscreen?
Consider the following criteria when choosing sunscreen:
- SPF Value: Minimum SPF 30 for daily use, SPF 50+ for outdoor activities
- UVA Protection: PA++ or PA+++ is the minimum recommended
- Broad Spectrum: Product label should state "Broad Spectrum"
- Filter Type: If sensitive skin, choose physical/mineral filter; if normal skin, choose a hybrid formula
- Texture: For face, serum or gel-cream; for body, thicker formulas can be chosen
- Water Resistance: If swimming or sweating is expected, choose a water-resistant product
- Skin Type Compatibility: Choose hybrid formulations that are non-comedogenic (pore-blocking), contain new generation chemical filters combined with physical filters, and have low irritant potential
How and How Much to Apply?
Application Amount
At least 1/4 teaspoon (approximately 0.5 ml) of sunscreen should be used for the face and neck. Dermatological tests show that this amount is needed to achieve the effective SPF value. Most people apply an insufficient amount, which leads to weak protection — this is the most common sunscreen application mistake.
Application Order
For a daytime routine with a UV index of 2 or higher, the following order is recommended:
- Cleansing
- Toner/Essence (if applicable)
- Serum (if applicable)
- Day Cream / Moisturizer
- Sunscreen (last step, proceed with makeup after 15 minutes of waiting)
Reapplication
Sunscreen should be reapplied after water activities, sweating, and even without these, every 2-3 hours at the latest. If applying over makeup is difficult, you can opt for sunscreen sprays or compact products with sun filters for reapplication.
Year-Round Routine
- Summer (May-October): SPF 50+, PA+++ or PA++++, reapply every 2 hours, and if you sweat a lot, choose water and sweat-resistant products for daily use
- Late Spring / Early Autumn: SPF 40-50, PA++, reapply every 3 hours
- Winter (November-April): SPF 30–50, PA++, daily morning application is sufficient (reapplication critical for outdoor activities)
- Cloudy days: SPF 30 minimum, SPF 50 can be chosen depending on the UV index
- In the Office/Indoor: SPF 30 is sufficient; those exposed to natural light (by a window) should prefer SPF 50
Sunscreen at Medicblu
Genosys Ultra Shield Sun Cream — SPF 50, PA+++
At Medicblu, you can find many sunscreen alternatives formulated with physical, chemical, and hybrid filters. You can easily find the right sunscreen for you by using the filtering options or get support from our experts via our corporate 850 line using the 'Consult an Expert' option.
Frequently Asked Questions (FAQ)
Q: Should sunscreen be applied every day?
A: Yes. Regardless of the weather, season, or your plans, you should use sunscreen if you are going outdoors. UV rays reach our planet every day of the year and cause cumulative damage.
Q: Is sunscreen necessary indoors?
A: Generally, SPF 30 is sufficient indoors. However, if you are working by a window or near an open window, choose SPF 50. Glass blocks 99% of UVB but allows 75-90% of UVA to pass through.
Q: Is SPF 30 sufficient, or SPF 50?
A: SPF 30 may be sufficient for daily use, but studies show that those who use SPF 50 have a lower risk of cancer. For outdoor activities, the beach, or prolonged UV exposure, choose SPF 50+.
Q: Can sunscreen be used with retinol?
A: Yes, it is important to use it. Retinol increases the skin's UV sensitivity, so those using retinol should use high SPF (50+) sunscreen. Use SPF 50 in the morning routine and retinol in the night routine.
Q: How often should sunscreen be reapplied?
A: Immediately after water activity or heavy sweating. For direct skin exposure, every 2 hours; for winter months or indoor use, morning application is sufficient. If you stay in the office all day, reapplication every 2 hours is not necessary.
Q: If my face cream contains SPF, do I need additional sunscreen?
A: Generally, yes. The SPF in face creams is usually low (typically SPF 15-25), and the application amount is often insufficient. For effective protection, it is recommended to use a dedicated SPF 30+ sunscreen.
Conclusion
Sunscreen is the most effective and proven method of protection against aging. Photoaging, pigmentation, DNA damage, and cancer risk caused by UVA and UVB radiation can only be prevented with regular sun protection. Choose hybrid formula products that provide SPF 30–50 and PA++ or higher protection, make it a strict habit in your morning routine, and reapply every 2 hours.
Sun protection is not a decision made today, but a lifelong habit. The investment you make in your skin in your 20s and 30s will be the most valuable gift in your 50s and 60s.
Scientific References
- Lim HW, Arellano-Mendoza MI, Stengel F. Sunscreens and Photoprotection. StatPearls. NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK537164/
- Sunscreens Part 1: Mechanisms and Efficacy (2024). J Am Acad Dermatol. https://www.jaad.org/article/S0190-9622(24)00785-0/abstract
- Lawrence KP et al. Improved photoprotection in the UVA/visible radiation boundary region is essential to prevent DNA damage, oxidative stress and gene expression changes in human skin. JEADV Clin Pract. 2025. https://doi.org/10.1002/jvc2.586
- Moyal DD, Fourtanier AM. Broad-spectrum sunscreens provide better protection from solar ultraviolet-simulated radiation and natural sunlight-induced immunosuppression in human beings. J Am Acad Dermatol. 2008;58(5 Suppl 2):S149-54. PMID: 18410801
- Guan LL, Lim HW, Mohammad TF. Sunscreens and Photoaging: A Review of Current Literature. Am J Clin Dermatol. 2021;22(6):819-828. PMID: 34387824
- Cayrol C et al. A mineral sunscreen affords genomic protection against ultraviolet (UV) B and UVA radiation: in vitro and in situ assays. Br J Dermatol. 1999;141(2):250-8. PMID: 10468796
- Brar G et al. A Comprehensive Review of the Role of UV Radiation in Photoaging Processes Between Different Types of Skin. Cureus. 2025;17(3):e81109. PMID: 40276407
