Sunburn at Altitude: Why Kids Burn Faster on Snow

Snow reflects UV back at you in a way sand and grass simply do not. The World Health Organization's own reflectance figures put fresh snow at as much as 80 percent, against under 10 percent for grass, soil and water and about 15 percent for sand. Germany's federal radiation protection authority, the Bundesamt für Strahlenschutz, puts fresh snow higher still, at up to 90 percent.

Altitude adds to that, by an amount the authorities themselves disagree about. Add a child, who the WHO says is particularly vulnerable to UV harm because of their skin and eye structure, and you have the whole problem in one sentence.

What to do about it is not contested at all. Broad spectrum sunscreen at high SPF on every exposed patch, applied under the nose and jaw as well as over them. A lip product with sun protection, reapplied like sunscreen. And eyewear carrying a CE mark plus UV400 or 100 percent UV protection, which every body we checked applies to children and adults alike.

The reason a ski day burns differently is not that the sun is fiercer than it is at the coast in August. It is that snow is the most reflective surface a family ever spends a whole day standing on.

The WHO publishes a comparative table of surface reflectance and ties it directly to the eye injuries that keep turning up in skiers. The American Academy of Dermatology uses the same 80 percent figure and describes the effect as effectively doubling your exposure. That is the framing worth carrying up the mountain: your child is being lit twice, once from the sky and once from the ground.

The precise percentage is one of the honest wobbles in this topic. Three otherwise authoritative bodies give three different numbers for the same phenomenon, which is why we have listed them separately rather than picking a favourite.

You will see a confident single figure repeated everywhere: the sun is 10 percent stronger for every 1000 metres you climb. It is a real number from a real authority. It is also not the only real number from a real authority, and the spread is wider than the confident version admits.

The German speaking Alpine bodies cluster tightly. The Bundesamt für Strahlenschutz says about 10 percent per 1000 metres. The Deutscher Wetterdienst, Germany's national weather service and the operator behind its UV Index forecasting, gives 8 to 10 percent. MeteoSchweiz, quoted by the Swiss Alpine Club, gives 10 to 12 percent. The Swiss Cancer League's Graubünden chapter says about 10 percent.

Then the foundational document behind every national UV Index programme, the Global Solar UV Index practical guide published jointly by the WHO, the World Meteorological Organization, UNEP and ICNIRP, says something materially different: about 5 percent per kilometre in clean air. That is roughly half what the German and Swiss bodies publish, from the organisation their UV Index programmes are built on.

And there is a unit trap waiting for anyone who reads across the Atlantic. American sources quote the effect per 1000 feet, not per 1000 metres. Boulder Community Health, a Colorado community hospital, gives 4 to 5 percent per 1000 feet. A thousand feet is roughly 305 metres, so that is a steeper gradient than it looks, not a gentler one. Anyone who reads a US figure as if it were metric will understate the effect by a factor of three.

The research does not explain the disagreement, so what follows is our reading of it. The altitude gradient is not a constant.

The WHO guide attaches an explicit condition to its figure: clean air. That condition is doing a lot of work. The gradient depends on how clean the air is and on the angle of the sun in the sky, which is one reason the same mountain reads differently in February and July.

One other thing is worth naming honestly. The older Swiss numbers come from a 2004 article, so they describe a stable physical relationship rather than a current measurement campaign.

For a sense of scale, the Swiss Alpine Club piece reports real UV Index readings alongside its gradient: 10 to 11 at Davos, at 1590 metres, and up to 13 at the Jungfraujoch, at 3580 metres. Those are summer readings. Winter sun sits much lower in the sky, so do not read a summer Index of 13 as your half term figure. If you want the resort itself, we cover it in the Davos Klosters resort guide.

Here is the useful conclusion. Whether the true figure is 5 percent or 12 percent per 1000 metres, nothing in your bag changes. There is no SPF you would choose at 12 percent and reject at 5 percent, and no goggle you would buy for one and not the other. The number is worth knowing so you can spot the sites that pretend it is settled. It is not worth agonising over.

This is the best sourced part of the whole subject, and it is unambiguous.

The WHO states in its ultraviolet radiation fact sheet that children and adolescents are particularly vulnerable to UV harm because of their skin and eye structure, that sunburns in childhood raise the risk of skin cancer in later life, and that a larger amount of UV can reach and damage their retina than an adult's.

Germany's federal public health institute, BIÖG, which runs the kindergesundheit-info child health service, adds the mechanism. Infant and toddler skin is thin, and the skin's own UV self protection has not yet developed in the first years of life. It names the head, and in particular the face, the neck and the ears, as especially sensitive. It also states that eyes react especially sensitively to sunlight, and it names mountain and snow conditions specifically as a setting where extreme UV-B can cause painful eye inflammation in children.

The Swiss Society of Paediatrics makes the same point about undeveloped self protection in skin and eyes, and adds the obvious one that adults forget: children are outdoors in the sun more than you are. That statement comes from a 2006 article in Paediatrica, so read it as a long standing principle rather than this season's guidance.

Translated for a ski week: your child has less built in protection than you do, is on the snow for as many hours as the lift runs, and cannot feel any of it happening.

What follows is our own reading of the reflectance figures above, not a claim we can attribute to any authority, and we would rather say that than dress it up.

If snow returns somewhere between half and 90 percent of the UV landing on it, then a child standing on a piste is lit from below almost as strongly as from above. Sunscreen habits are built at the beach, where the ground returns under 10 percent and everything you protect is a surface facing the sky. On snow, the geometry inverts. The underside of the nose, the chin, the soft skin under the jaw and the lower lip are all facing a floodlight.

The same logic explains the other surprise: ski sunburn does not announce itself. The usual explanation offered is that cold air and wind strip away the warmth cue you unconsciously rely on to know you have had enough sun. That is a reasonable inference rather than something we found stated by a radiation protection or dermatology body, so treat it as an explanation, not as a finding. Either way, the practical instruction is the same: on snow, do not wait to feel it. Our guide to how cold is too cold to ski with kids covers the other half of that same blind spot.

The BfS is the clearest of the official voices here. On its winter UV page it calls wraparound sunglasses with UV400 protection, UV400 ski goggles, or glacier goggles with UV400 protection indispensable for the mountains in winter. Note that it lists ordinary UV400 ski goggles as an equal option. You are not being told to buy mountaineering eyewear for a resort week.

Switzerland's Federal Office of Public Health, the BAG, gives the shopping instruction in one line: choose sunglasses marked CE and labelled 100 percent UV protection or UV400. On the American side, the American Academy of Ophthalmology asks for sunglasses or goggles blocking at least 99 percent of UV to prevent snow blindness, and recommends goggles with polycarbonate lenses for skiing, which also handle the wind and the impact risk. Different wording, same shelf.

Now the part that saves you money. The darkness of a lens is a separate label from its UV protection, and it is the UV label you are buying. The European standard EN ISO 12312-1 sorts lenses into filter categories by how much visible light they let through, and category 4 is the very dark glacier tint. Consumer standards explainers put category 4 at roughly 3 to 8 percent visible light transmission and say it is unsuitable for driving. We could not confirm that transmission band against the standard text itself or against a government body, so treat the exact figure as indicative rather than quotable.

What matters more is what we could not find. No body we checked publishes a different eyewear standard for children than for adults. Not the BfS, not the BAG, not the American Academy of Ophthalmology, not the American Academy of Dermatology. The UV400 and 100 percent requirement is age invariant in every source. If you see a page telling you children need a specific filter category that adults do not, it is inventing a distinction the authorities have not made.

Real talk: nothing in any of this official guidance mentions price or brand. It mentions a marking. Cheap goggles carrying CE and UV400 satisfy the same requirement that expensive ones do.

Both a European and a US authority pull lips out as their own item, which is unusual and worth noticing.

The BfS instructs that uncovered skin and the lips be protected with a broad spectrum sunscreen at a high to very high SPF. The American Academy of Dermatology asks for lip balm at SPF 15 or above, reapplied the way you reapply sunscreen, and notes that lips are very sensitive to sun damage. Where the two differ, the higher bar is the mountain one: SPF 15 is the AAD's general floor, while the BfS is writing specifically about winter at altitude.

You will often read that lips burn faster because they cannot produce melanin and lack the skin's natural fat and moisture film. That explanation is repeated near identically across German dermatology consumer sites, but we could not trace it to a dermatological society, the WHO, or a government body. Treat it as the common explanation rather than an established one. The instruction it supports is authority backed regardless: lips get their own product, and it gets reapplied.

Practical note for ski school mornings: a lip balm goes in the child's pocket or with the instructor, because the one in your jacket is on the wrong mountain by 10am. Our guide to kids' ski lessons and what to expect covers what else is worth handing over at drop off.

An overcast ski day feels like a day off from sun protection. It is not.

The Krebsliga Graubünden states that up to 80 percent of UV rays penetrate cloud cover. We should be straight with you about that figure: it is the only source we found putting a specific number on it, and it is a cantonal cancer league page rather than a federal one. Treat 80 percent as an order of magnitude rather than a measurement.

The underlying point is not in dispute anywhere, and it does not depend on the number. Cloud attenuates UV far less than it attenuates the light and warmth you actually notice, which is exactly why a flat grey day feels harmless. Combine that with snow throwing UV back up, and the overcast day is the classic one to get caught out on. Same routine, regardless of what the sky is doing.

Authority means saying what you can stop worrying about, so here it is.

The exact altitude percentage does not matter to you. It is contested between the WHO's own guide and the Alpine national bodies, and knowing that is useful mainly for spotting overconfident content. Nothing you pack changes between 5 percent and 12 percent.

You do not need glacier goggles for a resort week. The BfS lists UV400 ski goggles as an equal alternative to glacier goggles. If the goggles your child already owns carry CE and UV400, you are done.

You do not need a child specific lens category. No body we checked publishes one. The UV blocking requirement is the same at four years old as at forty.

A winter UV Index is not a summer UV Index. The eye watering readings quoted for high Alpine stations are summer figures. Your child is burning in February because of reflection, exposure hours and what is most likely a missing warmth cue, not because the Index is extreme.

And this is a solvable problem. Unlike most things that worry parents on a ski trip, this one is fully addressed by three items and a habit. Nobody has to ski less, go lower, or stay in.