Summer brings the highest levels of ultraviolet radiation of the year, subjecting the skin to multiple forms of damage—such as inflammation, dryness, pigmentation, and collagen breakdown. To avoid undermining the effects of whitening and anti-aging care, the key lies in choosing the right sunscreen and following evidence-based aftercare. This article, grounded in dermatological science, explains the basics of UVA/UVB, how to interpret SPF/PA ratings, the roles of filters and supportive ingredients, correct amounts and reapplication methods, usage tailored to skin type and lifestyle, a 24-hour aftercare timeline, and best practices for storage, hygiene, and expiration. It is designed as a practical guide you can use immediately, without needing additional explanations or supplementary notes—this is the complete version.

1. The Full Picture of UV Damage: What Happens to the Skin

Ultraviolet rays reaching the earth consist of UVA (320–400nm) and UVB (280–320nm).
UVA penetrates into the dermis, degrading collagen and elastin fibers, accelerating photoaging (wrinkles, sagging, enlarged pores).

UVB acts on the epidermis, causing acute inflammation such as redness, burning, and blistering (sunburn).

These effects are not temporary. Accumulated DNA damage prolongs pigmentation, leading to post-inflammatory hyperpigmentation (PIH) and persistent dullness. UV damage is not “just redness for a day,” but rather something that alters your skin condition for weeks or even months afterward. This is why prevention (protection) and recovery (repair) must be planned simultaneously.

2. How to Read SPF and PA: Don’t Choose by Numbers Alone

SPF (Sun Protection Factor) indicates protection against UVB.

PA (Protection Grade of UVA) indicates protection against UVA.

For summer outdoor activities, SPF50/PA++++ is generally recommended. However, it’s not just about the number—application amount, frequency of reapplication, and resistance to friction determine real effectiveness. Friction from sweat, towels, clothing, or masks quickly thins the sunscreen layer. Even with SPF50, thin application drastically reduces real protection.
For daily indoor life, SPF30/PA+++ is sufficient. But for long hours by the window, extended driving, or outdoor activity between 10 a.m. and 2 p.m., upgrading to PA++++ is worthwhile.

3. Types and Roles of UV Filters

Sunscreen protection comes from a combination of chemical (absorbing) filters and physical (scattering) filters.
Absorbers: Convert UV energy into heat or other harmless forms.

Scattering agents (zinc oxide, titanium dioxide): Reflect and scatter UV like a mirror.

Neither is absolutely superior—the formulation balance is key. Modern formulations minimize white cast while covering the long UVA1 range. Sensitive skin or children benefit from mineral-based (scattering-dominant) formulas, while those with oily skin or makeup concerns may find balanced chemical filters plus skin-conditioning agents more comfortable.

4. Supportive Ingredients: The Three Pillars of Hydration, Anti-Inflammation, and Antioxidation

UV protection isn’t complete with filters alone. Damage must be blocked at three levels:
Moisturizing: Ceramides, hyaluronic acid, glycerin maintain stratum corneum hydration and film uniformity.

Anti-inflammatory: Glycyrrhizic acid, allantoin, chamomile extract ease redness and stinging.

Antioxidants: Vitamin C derivatives, niacinamide, fullerenes, astaxanthin, and Coenzyme Q10 suppress free radicals and weaken pigmentation signals.

It is best if sunscreens contain these, but they can also be supplemented with aftercare products.

5. Choosing by Texture: A Formula You Can Use Consistently Is Best

Texture directly impacts compliance with the proper amount. If the formula feels greasy or leaves a white cast, people apply less. In sweaty summer months, gels, fluids, and light milks are practical. Use lighter formulas for oily T-zones, and richer milky types for dry-prone cheeks and neck. For makeup, check compatibility with primers and foundations, and prioritize formulas labeled “sweat-resistant” or “friction-resistant.” For outdoor sports, waterproof, rubber-like film types are effective.

6. Proper Amount, Application, and Reapplication: Turning Theory into Results

The ideal layer thickness equals about a 500-yen coin’s worth, or two fingers’ length (index and middle) for the entire face. Commonly missed areas include ears, temples, hairline, neck, nape, hands, feet, and lips. Shoulders and collarbones—where clothing rubs—need frequent touch-ups. Because sweat, sebum, and friction degrade the film, reapply every 2–3 hours. Over makeup, reinforce with UV sprays or powders. If towels are used frequently outdoors, touch up those areas immediately afterward. At the end of the day, use proper cleansing to fully remove the film and prevent clogged pores or irritation.

7. Scene-Specific Recommendations

Commuting/Indoor lifestyle: SPF30/PA+++ is sufficient. For long window exposure or driving, use PA++++.
Beach, pool, festivals, sports events: SPF50/PA++++ waterproof formulas. Plan reapplication for back of the neck, ears, shoulders.

High-intensity UV environments (mountains, fishing): Don’t forget UV protection for lips, scalp partings, and around the eyes.

Remote work at home: Avoid sitting with your back to a window, use UV-cut curtains to reduce reliance on sunscreen.

8. Tailoring to Skin Types and Life Stages

Sensitive skin: Choose low-irritant, fragrance-free, alcohol-free mineral formulas.

Oily/acne-prone skin: Non-comedogenic, lightweight emulsions are best.

Dry/aging skin: Opt for ceramides, squalane, amino acids for moisturizing support.

Children: Favor “soap-removable,” “water-resistant” formulas for ease and safety.

Pregnancy/breastfeeding: Select low-fragrance, low-irritant formulas, with frequent reapplication for safety.

Men: Sweat- and friction-resistant gels or sticks are practical.

9. Commonly Overlooked Areas: Lips, Scalp, and Eye Area

Lips: Thin stratum corneum makes them prone to dryness and lines—use UV lip balm by day, lip mask by night.

Scalp parting: Direct exposure hotspot—UV sprays are highly effective here.

Eye area: Thin skin, prone to film breakdown—combine sunscreen with sunglasses or wide-brim hats for additional physical protection.

10. Aftercare Timeline: The First 24 Hours Post-Sun Exposure

0–3 hours (Acute inflammation phase): Cool the skin with running water or cold towels for 10–15 minutes, repeat until stinging subsides. Avoid friction. Apply high-moisture gels (hyaluronic acid, aloe, glycerin). If needed, use lotions with glycyrrhizic acid or allantoin to calm inflammation.

3–24 hours (Barrier reconstruction): Apply ceramide cream to restore intercellular lipids and prevent water loss. Keep baths short and lukewarm, avoid harsh soaps, don’t peel off flaking skin. Small amounts of vitamin C derivatives can be introduced.

24–72 hours (Pigment suppression phase): Once redness subsides, use niacinamide and vitamin C derivatives to inhibit melanin production. Prioritize hydration if dryness persists, postpone strong retinoids. Always reapply sunscreen outdoors.

After 1 week (Long-term recovery): Support turnover with mild retinoids or PHAs. For persistent pigmentation, continue vitamin C and niacinamide for tone improvement.

11. Ingredient comparison: roles and the logic of selection

Moisturizing stabilizes the effective SPF by creating a uniform “film” of the stratum corneum. Hyaluronic acid retains moisture, ceramides replenish intercellular lipids, and urea provides moisture retention and softening. For anti-inflammatory care, glycyrrhizic acid, allantoin, and centella asiatica (CICA) are standard. For antioxidation, a two-axis approach with fast-acting vitamin C derivatives and sustained niacinamide is rational. For sebum regulation, niacinamide and L-carnitine; for calming sensitive skin, panthenol and β-glucan. For hair and scalp, tocopherol and polyphenols suppress daytime oxidative odor and color fading.

12. Common misconceptions and truths

“It’s SPF50 so no reapplication is needed all day” is a misunderstanding. The film is worn down by sweat, sebum, and friction, lowering the effective SPF. “You don’t need it on cloudy days” is also wrong. Even with clouds, a lot of UVA passes through. “Unnecessary indoors” also depends on the situation. While window glass blocks much of UVB, UVA passes through. Because light acts cumulatively, small daily exposures accelerate photoaging.

13. Layering with makeup: the order to prevent caking

Sunscreen → primer → foundation → UV powder is the basic order. After sunscreen, wait 30 seconds to 1 minute and proceed to the next layer once surface moisture has settled. For areas prone to caking such as the sides of the nose and the outer corners of the eyes, apply two thin coats to even out the film. For daytime shine, gently press with paper blotting sheets and reinforce with UV powder without rubbing. Mist toners are convenient, but it is important not to wet the skin so much that the film is destroyed.

14. Body operation design: the wider the area, the more planning is needed

The body has a large surface area, and missed spots and uneven application cause tanning. The shoulders, back, and décolletage are easily rubbed off by clothing, so apply two coats before going out. The backs of the hands are among the areas with the most UV exposure and are frequently rubbed by driving, shopping baskets, and smartphones, so carrying a small stick for targeted touch-ups provides realistic protection.

15. Detailed care for lips, nails, and around the eyes

Protect the lips with a UV lip product and provide intensive moisture at night with ceramides and shea butter. Nails tend to yellow and become brittle due to UV rays, so using a UV top coat is effective. Around the eyes, combine physical shielding with sunglasses and hats with low-irritation formulas to prevent fine lines caused by rubbing.

16. Sports and leisure specifications: sweat resistance, abrasion resistance, and chlorine resistance

Sports cause the film to deteriorate due to salt, sebum, and dust. Do not just choose waterproof types, but make reapplication at the timing when sweat has subsided a routine. In pools, chlorine easily breaks down the film, so following the sequence of fresh water shower immediately after getting out → light wiping → reapplication reduces failures. On beaches, the abrasive action of sand particles scrapes strongly, so touch-up application on the shoulders, front thighs, and shins is efficient.

17. The reality of the workplace: masks, uniforms, air conditioning

Wearing a mask breaks the film due to friction at the cheekbones and in front of the ears. Applying an additional thin layer to exposed areas after putting on the mask improves durability. On the neck where the collar of the uniform touches, switching from stroking application to pressing application makes it less likely to peel off due to friction. Direct airflow from air conditioning robs the stratum corneum of moisture, so applying light moisturizing → sunscreen before work is recommended.

18. Storage, hygiene, expiration: management to prevent reduced effectiveness

Sunscreen deteriorates with high temperatures and direct sunlight. Avoid leaving it in the car; store it at room temperature and in a dark place. After opening, use it up within one season as a guideline, and replace it if you notice odor or separation. Keep the nozzle from directly touching the skin or hands and keep it clean to help prevent skin troubles. For amounts to be taken to the sea or mountains, divide into smaller portions, and avoid exposing the entire bottle to blazing sunlight to enhance effectiveness.

19. Perspective of environment and safety

For leisure at the sea or rivers, actively combining physical shielding such as clothing, hats, parasols, and rash guards reduces the total amount applied while maintaining effective protection. If unsure about choosing a formulation, using clothing to limit the minimum necessary application area is the most universal and environmentally friendly measure.

20. Case study: the entire process of practical operation

Case A (midsummer beach outing with family): Apply two coats at home 30 minutes before departure → upon arrival, perform touch-up application on the shoulders, neck, in front of the ears, and backs of the hands → after coming out of the sea, rinse off sand with fresh water and pat dry → cool down with aloe gel → ceramide emulsion → lukewarm shower and low-irritation cleansing after returning home → at night, vitamin C derivatives + moisturizing.
Case B (outdoor sports spectating, 6 hours): Before starting, apply the specified amount of SPF50/PA++++ to the face, ears, neck, and hands → use hat and sunglasses together → before lunch, reapply with a UV stick on the cheekbones, nose, and backs of the hands → after finishing, cool → moisturize → soothe.
Case C (working from home + afternoon shopping): In the morning, apply SPF30/PA+++ with a lightweight gel → use curtains when working by the window → just before going out, add a touch-up to the cheekbones and tip of the nose → after returning home, wash with lukewarm water → toner → emulsion to finish.

21. Q&A: practical answers from an expert perspective

Q. I don’t like stickiness and end up applying a thin layer.
A. Changing the texture is the first choice. Switch to a gel or fluid, and secure the total amount with two thin layers applied separately.
Q. My skin peels after sunburn.
A. Do not forcefully peel it off; follow the order of cooling → moisturizing → soothing. Oil alone cannot lock in water, so first replenish water with a water-based gel or toner, then seal it with oils. Q. The dullness remains.
Q. Dullness remains.
A. Early soothing is important to shorten the tail of inflammation. From a few days later, suppress the signals of melanin synthesis with vitamin C derivatives and niacinamide, and support stratum corneum turnover at night with ample moisturizing.

22. Mini comparison: “formulation strengths” by use case

Non-chemical formulas are strong in managing low irritation and the risk of white cast. Absorber-dominant formulas are advantageous for lightness and compatibility with makeup. Gels are comfortable in summer, milks are good for dryness, sticks are convenient for reapplication and targeted reinforcement. Sprays are suitable for hair and back; for film uniformity, the extra step of close-range spraying → smoothing with hands is effective.

23. Final checklist for a purchase that won’t fail

• Prioritize compatibility with your skin type (irritation, stickiness).
  
• Design your routine by combining shapes that are easy to reapply (sticks, mini sizes).
  
• Decide which of moisturizing, soothing, and antioxidation will be handled by the sunscreen and which by aftercare, and assemble the lineup for overall optimization.
  

24. One-day operation sample (summer, normal skin)

In the morning, prepare the stratum corneum with a low-irritation toner → ceramide emulsion, and apply two fingers’ worth of SPF50/PA++++. For makeup: primer → thin-layer foundation → UV powder. At noon, press with blotting paper → UV powder. On days with a lot of outdoor movement, add a stick to the nose and cheekbones. After returning home, take a lukewarm shower → low-irritation cleansing; for the body, wrap with foam. At night, aloe gel → vitamin C derivatives → ceramide cream before bed. Include gentle exfoliation twice a week to prevent dullness from setting in.

Summary: “design” protection and recovery

Summer skincare succeeds by designing three stages along your daily workflow: ① protect (filters, physical shielding), ② regulate (moisturizing, soothing), and ③ recover (antioxidation, keratolytic care). While SPF and PA numbers are important, the operational details—amount applied, reapplication, friction resistance, and removal—determine the results. Reduce inflammation quickly and keep pigment from being produced or accumulating. If you fit sunscreen and aftercare products into your day according to this principle, you can maintain translucent, firm skin even under the strong summer sun.