Expert Guide to Sun Protection: Choosing Between Chemical and Mineral Sunscreens

Protecting your skin from the sun is vital for preserving your long-term health. Discover how to select the ideal sunscreen, comparing chemical and mineral filters.

Why Protect Yourself from the Sun?

Solar radiation contributes to numerous diseases. Limiting excessive sun exposure can prevent 4 out of 5 skin cancers.

The Sun's Rays

Within the light spectrum, ultraviolet (UV) rays lie beyond violet and are invisible. There are three types:

• UVA: Accounts for 95% of UV rays reaching Earth's surface. They penetrate deep into the dermis, causing immediate but fleeting pigmentation. UVA rays drive long-term damage like skin aging and cancer, and they pass through glass (windows, etc.).

• UVB: Makes up 5% of UV rays reaching Earth. They affect the epidermis, leading to sunburn, skin thickening, and tanning. UVB rays are blocked by glass.

• UVC: The most dangerous, but mostly absorbed by the ozone layer, so they don't reach Earth's surface.

Is a Tan Natural Protection?

The skin has two primary defenses against sun exposure:

• Thickening of the stratum corneum: hyperkeratosis.

• Melanic pigmentation: the tan.

A tan provides limited UVB protection (equivalent to SPF 6 at most) but offers no defense against UVA.

Self-tanners and tan accelerators do not provide UV protection.

Food supplements promising a tanned look or prevention of sun allergies (lucite) do not protect against UV rays.

Sun Capital: A Resource Not to Squander

Your sun capital—the skin's unique defenses against solar damage—varies by individual and depends on:

• Intensity and duration of lifetime sun exposure: Exposures before age 20 pose the highest risk. Children under 2 should never be exposed to direct sunlight!

• Phototype: Skin's sun sensitivity, from type 1 (very fair skin) to type 4 (dark skin).

To learn more about best practices for sun protection, click here.

How to Prevent Sun Risks

The UV index guides the appropriate level of sun protection. Protect yourself whenever it's above 3.

Solar Avoidance

UVA exposure remains steady throughout the day, but UVB varies by:

• Time of day: In summer, from 12 p.m. to 4 p.m., the sun is at its peak, allowing more UVB through with less atmospheric filtering.

• Clouds: Thick clouds filter rays, but even overcast skies let through 95% of radiation despite cooler sensations.

• Altitude.

• Reflection: Water and white surfaces reflect up to 85% of rays. Under a parasol, 50% of UV passes through; sand reflects 15-20%.

Covering Clothing

• Darker clothes offer superior protection, though they absorb infrared and feel warmer. Wet or damp clothes (from sweat) block UV less effectively.

• Category 3 sunglasses (strong light) or category 4 (extreme light) are essential for eye protection. Category 4 suits babies and young children.

Using Sunscreen

Effective sunscreens must shield against both UVA and UVB:

• UVB protection indicated by SPF (Sun Protection Factor).

• UVA protection at least one-third of the SPF, covering peak UVA wavelengths.

Sunscreens labeled with SPF and UVA meet these standards.

Choose protection levels based on phototype. Categories include:

- Low: SPF 6 or 10

- Medium: SPF 15, 20, or 25

- High: SPF 30 or 50

- Very high: SPF 50+

Photosensitizing medications demand enhanced protection; consult your pharmacist or doctor.

Apply sunscreen before exposure to all uncovered areas, including hands, ears, temples, and feet. For an average adult, use about 36g (6 teaspoons).

Reapply every 2 hours and after swimming, toweling, or sweating. No protection extends exposure time indefinitely.

Sun Protection Products: Chemical vs. Mineral Filters

Sun creams and lotions are cosmetics with chemical and mineral filters that block UV rays.

Chemical Filters

These absorb UV rays, with efficacy tied to their spectrum:

• Narrow-spectrum: UVB only.
• Broad-spectrum: UVB and UVA.

They may cause irritation or allergies, worsened by frequent reapplication. Most problematic include:

• Benzophenone (oxybenzone)*
• 4-Methylbenzylidene camphor (4-MBC)* and 3-BC (3-benzylidene camphor)*
• Para-aminobenzoic acid (PABA) derivatives
• Octocrylene

*Endocrine disruptors.

Avoid chemical filters on broken or injured skin, and in infants.

They can harm marine life (fish, corals). Opt for eco-friendly formulations.

Mineral Filters

These reflect and scatter UV rays. They're photostable, low-allergy, and non-toxic. Key ones:

• Titanium dioxide
• Zinc oxide

They can leave a white cast and feel less fluid.

Often nano-sized (1-100 nm; DNA is ~2 nm) for easier application without residue.

EU deems nanoparticles safe up to 25% concentration on intact skin (EC Regulation 1223/2009).

ANSM advises against on damaged or sunburned skin.

Since 2013, nanoparticles are labeled, e.g., titanium dioxide [nano].

Ideal for infants, children, pregnant women, and sensitive skin—prefer non-nano, eco-labeled mineral options.