Photoprotection

Sunlight is the leading external cause of photoaging, DNA damage in keratinocytes, chronic hyperpigmentation and skin cancer. Photoprotection is much more than applying an off-the-shelf sunscreen. It is a layered medical strategy that combines chemical and mineral UV filters, antioxidants that work inside the cell, protection against visible light (VIS) and infrared A (IRA), and physical measures.

At Haute-Derma, photoprotection is a required foundation of every dermatology treatment plan, from barrier repair and melasma or pigment treatment to aftercare following procedures such as laser, chemical peels and microneedling. A medical-grade sun protection plan is tailored to each patient's Fitzpatrick skin type, the radiation they are exposed to and their individual skin profile.

How Solar Radiation Affects the Skin

UVB (290–320 nm): makes up about 5% of the UV energy reaching Earth and acts mainly on the epidermis. UVB directly causes DNA damage in the form of cyclobutane pyrimidine dimers (CPDs), triggers sunburn (erythema) and is the main driver of basal cell carcinoma (BCC) and squamous cell carcinoma (SCC).
UVA (320–400 nm): accounts for 95% of UV radiation and reaches deep into the dermis. UVA generates reactive oxygen species (ROS) and switches on matrix metalloproteinases (MMPs), enzymes that break down collagen and elastin. UVA1 (340–400 nm) is a key trigger for melanin production in pigment cells, driving melasma and post-inflammatory hyperpigmentation (PIH).
High-energy visible light (HEVL / blue light, 400–500 nm): penetrates deeper than UVA and stimulates opsin receptors (opsin 3) on pigment cells. In people with darker skin types (Fitzpatrick III–VI), it causes pigmentation that is darker and lasts considerably longer than UVA-induced pigmentation.
Infrared A (IRA, 700–1400 nm): reaches as far as the subcutis, raises tissue temperature, disrupts the mitochondrial electron transport chain and increases MMP-1 release, which leads to skin laxity.

Types of Photoprotective Filters and How They Work

Mineral (Inorganic) Filters: titanium dioxide (TiO2) and zinc oxide (ZnO).
- How they work: they reflect, scatter and absorb UV radiation.
- Key features: zinc oxide gives excellent broad-spectrum coverage across UVB, UVA2 and UVA1. It is very gentle and non-irritating, making it a good choice for sensitive skin, skin after procedures and children.
New-Generation Chemical (Organic) Filters: Tinosorb S (bis-ethylhexyloxyphenol methoxyphenyl triazine), Tinosorb M, Uvinul A Plus, Mexoryl SX/XL.
- How they work: they absorb the photon energy of UV rays and release it as harmless heat.
- Advantages: highly photostable (they do not break down in sunlight), leave no white cast and cover both UVA and UVB.
Visible Light (HEVL) Filters: iron oxides (Fe2O3, Fe3O4).
- How they work: they block blue light (400–500 nm) from penetrating the skin. Iron oxides are an essential ingredient in tinted sunscreens used to treat melasma.
Antioxidants and Intracellular DNA Repair: vitamin C, vitamin E, ferulic acid, niacinamide, Polypodium leucotomos, photolyase.
- How they work: they mop up ROS, neutralize free radicals generated by IRA and visible light, and help the photolyase enzyme repair UVB-induced DNA damage.

Comparing Sun Protection Ratings and Filter Ingredients

Rating / Ingredient	How It Is Measured / How It Works	Main Clinical Use
SPF	Compares the time to skin reddening (erythema) with and without sunscreen	Preventing sunburn and epidermal aging
PA / PPD	Measures persistent pigment darkening of the skin	Preventing melasma, PIH and dermal aging
Iron oxides	Absorb and scatter 400–500 nm light	Melasma, PIH, hyperpigmentation in Fitzpatrick III–VI skin
Zinc oxide (nano/non-nano)	Absorbs and reflects 290–400 nm radiation	Skin after laser or peels, contact dermatitis, children
Tinosorb S / Uvinul A Plus	Absorb photon energy; highly photostable	New-generation sunscreens for skin under treatment

Clinical Safety, Environmental Impact and Practical Tips

The Photostability Challenge: older chemical filters such as avobenzone break down readily in light, losing up to 50% of their effectiveness after one hour of sun exposure. Pairing avobenzone with octocrylene, or using newer filters such as Tinosorb S, keeps the formula stable.
Impact on Marine Ecosystems (Coral Reef Safety): traditional chemical filters such as oxybenzone (BP-3) and octinoxate (EHMC) have been shown to contribute to coral bleaching. Switching to mineral filters (non-nano zinc oxide) or newer organic filters helps protect the marine environment.
Eye Irritation and Allergic Contact Dermatitis: filters such as octocrylene or avobenzone can sting the eyes or cause allergic contact dermatitis in people with sensitive skin.
Pigmentary Conditions: in melasma treatment, untinted sunscreens without iron oxides often fail to prevent relapse because they do not block blue light from the sun and from electronic screens.

Our Photoprotection Protocol at Haute-Derma

Assessing Skin Type and Sun-Related Risk

Determine the Fitzpatrick skin type (I–VI), any history of light sensitivity, precancerous lesions (actinic keratoses) and existing pigmentation.
Review daily habits, time spent in the sun and work environment (outdoors or in front of a screen).

Building a Layered Sun Protection Plan

The Right Amount: we show patients how to apply the standard dose of 2 mg/cm2, about 1.25 ml, or the "two-finger rule" for the whole face.
For Melasma and Hyperpigmentation: a tinted sunscreen with iron oxides plus zinc oxide, combined with a new-generation UVA1 filter.
For Skin After Procedures (Laser/Peel): a mineral-only formula (zinc oxide, titanium dioxide) with soothing, restorative ingredients such as panthenol and Centella asiatica to avoid irritation.
Oral Sun Protection: add Fernblock (Polypodium leucotomos extract) or oral glutathione/niacinamide to raise the minimal erythema dose (MED) from within.

Reapplication and Follow-Up

Reapply sunscreen every 2 hours during continuous outdoor activity, and right after swimming or heavy sweating.
Return after 8–12 weeks to reassess melanin levels and sun damage with advanced skin imaging.

Frequently Asked Questions (FAQs)

+Why should people with melasma choose a tinted sunscreen containing iron oxides?

High-energy visible light (HEVL, or blue light) in the 400–500 nm range reaches deep into the dermis and activates opsin 3 receptors on pigment cells, causing strong, long-lasting melanin production in Asian skin (Fitzpatrick III–IV). Standard UV filters, even at SPF 50 or PA++++, do very little against HEVL. The iron oxides that give tinted sunscreens their color absorb and physically block this light, which helps prevent melasma from coming back.

+Will wearing sunscreen every day leave me seriously low in vitamin D?

Real-world clinical studies show that daily sunscreen use does not cause vitamin D deficiency in healthy adults. In practice, most people apply only about 0.5–1 mg/cm2 (roughly 25–50% of the standard dose), so a small amount of UVB still gets through the skin, enough to make vitamin D. In addition, about 10–15 minutes of sun on the arms and legs a few times a week meets most people's needs, and vitamin D is also easy to get from food or supplements.

+Is nano zinc oxide in sunscreen toxic to the body?

Nano zinc oxide was developed to reduce the white cast on the skin while keeping broad-spectrum protection. Safety reviews by the EU Scientific Committee on Consumer Safety (SCCS) and the FDA indicate that nano zinc oxide particles stay mainly in the outermost layers of the stratum corneum on intact skin and penetrate the epidermal barrier into the bloodstream to a negligible extent, if at all. Sunscreens containing nano zinc oxide are therefore considered safe on intact skin.