UVA all year round: why protection doesn't stop in winter

Reading time: 6-8 min

Important note: this article provides general cosmetic and scientific information. It is not a substitute for medical advice and does not constitute a diagnosis.

Introduction

In winter, many people relax their sun protection. The sky is gray, the sun seems "weak", and the idea settles in: "UV is no longer an issue."

Yet science reminds us of an essential nuance: UVA rays don't disappear in winter. They are present from morning to night, pass through clouds more easily than UVB, and contribute to skin ageing (photoaging) as well as to certain pigmentary irregularities.

The aim of this article is simple: to understand what the studies really show, and then to draw up a coherent protection strategy, without overkill, using a methodical approach.

UVA vs. UVB: not the same "danger", nor the same seasonality

UVB rays are more variable: they rise sharply in summer, at midday, and more easily trigger erythema (sunburn). UVA, on the other hand, is more constant throughout the day and year.

Two very practical consequences:

• In winter, you may not "burn"... but still receive a significant dose of UVA.
• Anti-ageing" and "anti-dark spot" protection rely heavily on good UVA coverage (in addition to UVB).

Why UVA remains an issue in winter

1) UVA penetrates clouds more easily

Field measurements of UVA show that cloud cover influences irradiance, but does not cancel it out. In other words: overcast skies may reduce exposure, but they don't cancel it out, especially for UVA.

2) UVA penetrates deep into the skin

The literature on photoaging emphasizes that UVA penetrates deeper than UVB, to the dermis, and contributes to mechanisms associated with extrinsic aging: oxidative stress, alterations to the dermal matrix, progressive loss of firmness.

3) Snow, mountains, reverberation: winter can sometimes increase exposure

In alpine conditions, UV irradiance can increase with altitude, and snow can reinforce exposure via reflection. Modelling work and UVA measurement networks even show that, in certain mountain contexts, UVA exposure in winter can be significant.

"I'm often indoors": why that's not enough to rule out UVA exposure

Much of modern daily life is spent indoors... but there's one point that's often overlooked: some lenses transmit some UVA (whereas they are much better at blocking UVB).

Publications on photoprotection by glass (windows, automotive) confirm that UVA transmission depends on the type of glass (laminated, tempered, films, tints). In some cases, UVA transmission can remain significant.

This is not a call to live in fear. It's a guideline: if you're near a bright window, if you drive a lot, or if your skin is prone to spots, redness or cosmetic photo-sensitivity, well-chosen daily protection makes sense.

UVA and skin ageing: what research best supports

UVA rays are strongly implicated in photoaging: they generate oxidative stress, promote inflammatory pathways and participate in the progressive degradation of dermal components important for firmness.

And above all: studies on the efficacy of sunscreen in preventing skin ageing are moving in a clear direction. A randomized trial in middle-aged adults showed that regular use of sunscreen slows down clinically-measured skin aging.

The most rational winter strategy: protect without weighing down

Successful winter protection is what you hold on to. It must therefore be :

• comfortable (no "impossible-to-wear" greasy effect),
• stable (easy, even application)
• broad spectrum (UVB + UVA).

1) Choose broad-spectrum protection (including UVA)

In practice, look for a mention of broad spectrum and a credible level of UVA protection (according to local standards). If your objective is "anti-aging / anti-spot", the UVA dimension becomes central.

2) Adjust quantity and reapplication to real life

The most useful cosmetic rule: protection depends as much on the formula as on the quantity applied. In winter, if you're mainly indoors, one application in the morning may be enough for many people. If you're outdoors for long periods (walking, on the terrace, skiing), reapplication becomes essential.

3) Don't forget the "gentle cleansing + stable barrier" duo

Comfortable skin is better able to tolerate daily sun protection. In winter, if you're tempted to "strip" to remove SPF, you risk damaging the barrier and increasing reactivity.

The most elegant solution is often a precise, gentle evening routine (e.g. double cleansing if necessary), followed by an adapted moisturizing/barrier.

Things to remember

• UVA rays are present all year round and contribute to skin ageing.
• Overcast skies can reduce exposure, but do not eliminate UVA.
• Snow, altitude and certain winter environments can increase exposure via reflection and atmospheric conditions.
• Some lenses transmit some UVA: "being indoors" does not mean "zero UVA".
• The most rational strategy in winter: pleasant broad-spectrum protection, worn regularly, and barrier-friendly evening cleaning.

Scientific sources

• Wilson BD, Moon S, Armstrong F. Comprehensive Review of Ultraviolet Radiation and the Current Status on Sunscreens (2012) (PMC).
• Hughes MCB et al. Sunscreen and prevention of skin aging: a randomized trial (2013).
• Guan LL, Lim HW, Mohammad TF. Sunscreens and Photoaging: A Review of Current Literature (2021) (PMC).
• Tuchinda C et al. Photoprotection by window glass, automobile glass, and sunglasses (2006).
• Almutawa F et al. Current status of photoprotection by window glass, automobile glass, and window films (2013).
• Duarte I et al. The role of glass as a barrier against the transmission of ultraviolet radiation (2009).
• Sabburg J, Parisi AV. Effect of cloud on UVA and exposure to humans (2001).
• Schmalwieser AW et al. The Austrian UVA-Network (2019) (PMC).