My mother grew up on the coast, in the years when a tan was proof you had spent your summer well. She has photographs of herself at nineteen lying on a towel with baby oil on her shoulders and a reflector under her chin. Nobody wore hats. Nobody knew. She is 74 now and has had eleven skin cancers removed: nine basal cell carcinomas, one squamous cell carcinoma on the back of her hand, and one melanoma, caught at 0.6 millimetres deep on her calf because a locum GP happened to ask about a mole she had been ignoring for a year. She is fine. She is also a walking map of every sunburn she ever had, and every time I take my own children to the beach I think about her towel.
I am writing this because most advice on how to prevent skin cancer is either so vague it is useless ("be sun safe") or so strict that nobody follows it. What follows is the middle path: the types of skin cancer and how common they really are, the risk factors ranked by how much they matter, the single randomised trial that proved sunscreen works, how to actually check your own skin, and what the evidence says about diet, weight, vitamin D and the sunbed question. Every figure is linked to its source. None of it requires living in the dark.
How common skin cancer is, and why the numbers keep climbing
Skin cancer is the most common cancer in the world, and it is not close. In the United States more than five million skin cancers are treated every year, more than all other cancers combined (American Cancer Society). Around 105,000 of those are invasive melanomas, the type that kills, and melanoma takes roughly 8,000 American lives a year. In the UK, melanoma is the fifth most common cancer and its incidence has more than doubled since the early 1990s (Cancer Research UK).
There are three types you need to know about, and they behave very differently:
| Type | Share of cases | Where it comes from | How dangerous |
|---|---|---|---|
| Basal cell carcinoma (BCC) | About 75 percent | Cumulative sun over decades, usually on the face, ears, neck | Almost never spreads, but eats into local tissue if ignored |
| Squamous cell carcinoma (SCC) | About 20 percent | Cumulative sun, plus immunosuppression, old scars, HPV | Can spread in 2 to 5 percent of cases, more in high risk sites |
| Melanoma | About 1 to 5 percent | Intermittent intense sun and burns, sunbeds, genetics | Responsible for most skin cancer deaths; curable if caught early |
The rise is not mysterious. Cheap flights, outdoor leisure, sunbeds, and a generation of children who burned before anyone knew better. The cheering part is the Australian curve. Australia has the highest rates on earth, and yet melanoma in Australians under 40 has been falling since the mid 2000s, because the people who were children during the Slip Slop Slap campaigns grew up with less damage (Aitken et al., International Journal of Cancer 2018). Prevention works on a national scale. It also works on the scale of one family.
What causes skin cancer: the risk factors ranked
Ultraviolet radiation causes around 86 percent of melanomas and 90 percent of non melanoma skin cancers (Parkin et al., British Journal of Cancer 2011). Within that, the pattern of exposure matters. Basal cell and squamous cell cancers follow the total dose: farmers, sailors, builders, golfers. Melanoma follows the pattern of intermittent intense exposure and burning: the office worker who spends fifty weeks indoors and two weeks going pink in Spain.
Sunburn, especially early
Five or more blistering sunburns between the ages of 15 and 20 raised melanoma risk by 80 percent and basal cell risk by 68 percent in a cohort of more than 100,000 nurses followed for two decades (Wu et al., Cancer Epidemiology, Biomarkers and Prevention 2014). Childhood skin is not just thinner; a burn at ten leaves mutations that have sixty years to accumulate company.
Sunbeds
A meta analysis of 27 studies found that ever using a sunbed raised melanoma risk by 20 percent, and first use before age 35 raised it by 59 to 75 percent (Boniol et al., BMJ 2012). The authors estimated that sunbeds cause about 3,400 melanomas a year in Western Europe alone. The World Health Organization classifies them as a group 1 carcinogen, the same category as tobacco. There is no safe base tan.
Skin type, hair colour, moles and family
Fair skin that burns and never tans roughly doubles melanoma risk, red hair (the MC1R gene) more than doubles it even without burning, and having more than 100 ordinary moles raises it about sevenfold (Gandini et al., European Journal of Cancer 2005). A parent, sibling or child with melanoma raises your own risk by about 74 percent, and about 10 percent of melanomas run in families. If two or more close relatives have had melanoma, ask about referral to a genetics service; CDKN2A mutations are worth knowing about.
A weakened immune system
Organ transplant recipients on immunosuppressant drugs have a 65 to 250 fold higher risk of squamous cell carcinoma (Euvrard et al., NEJM 2003). If you take methotrexate, azathioprine, biologics or long term steroids for another condition, you belong in the higher risk group and should have yearly skin checks.
Darker skin is not immune
Melanoma is around 20 times less common in Black Americans than in white Americans, but when it occurs it is diagnosed later and five year survival is lower, about 70 percent compared with 94 percent (American Cancer Society). In people with brown and black skin, melanoma tends to appear on the palms, soles, under the nails and in the mouth, places the sun never reaches. Bob Marley died of a melanoma under a toenail that was mistaken for a football injury. Everyone should check their feet.
Does sunscreen prevent skin cancer? The Nambour trial
For years people argued about whether sunscreen prevented cancer or simply let people stay out longer. Then came Nambour. In the Queensland town of that name, 1,621 adults were randomised in 1992 either to apply SPF 15 sunscreen to the head, neck, arms and hands every morning, or to use sunscreen as they normally would. After four and a half years the daily group had 39 percent fewer squamous cell carcinomas (Green et al., Lancet 1999). Ten years after the trial ended, when the researchers went back, the daily group had developed half as many melanomas and 73 percent fewer invasive melanomas (Green et al., Journal of Clinical Oncology 2011). It remains the only randomised trial of sunscreen and melanoma ever completed, and its result is the reason every dermatologist you meet will say the same thing: daily, not occasionally.
What that looks like in practice:
- SPF 30 or higher, broad spectrum (UVA and UVB). The step from SPF 30 to 50 matters less than the step from applying a fifth of the right amount to applying enough.
- Enough of it. Two milligrams per square centimetre, which is about half a teaspoon for the face and neck and a full shot glass (35 ml) for the whole body. Most people apply a quarter to a half of that, which turns SPF 30 into about SPF 8 (Petersen and Wulf, Photodermatology 2014).
- Every two hours outdoors, and after swimming or sweating regardless of the label.
- Every day the UV index is 3 or above, which in the UK is April to September and in most of the US is most of the year. Check the forecast; your weather app shows it.
- Mineral or chemical, whichever you will wear. Zinc oxide and titanium dioxide suit sensitive skin and children. Modern chemical filters are safe at the doses absorbed; the FDA's 2020 absorption study found systemic levels above its testing threshold, which triggered more study, not a warning (Matta et al., JAMA 2020).
Shade, clothing and timing do more than sunscreen
Sunscreen is the last line, not the first. Dermatologists rank protection in this order because it matches how reliably each one works when a real person uses it:
- Timing. Plan the run, the gardening and the beach for before 10 or after 4 when you can. The shadow rule is a good shortcut: if your shadow is shorter than you are, the UV is strong.
- Shade. Trees, umbrellas, awnings. Remember that sand, water and snow reflect 15 to 80 percent of UV back up under the umbrella, so shade at the beach halves exposure rather than removing it.
- Clothing. A dry cotton T shirt is about UPF 5 to 7; wet, it is 3. A long sleeved rash vest rated UPF 50 blocks 98 percent. Dark, tightly woven, dry fabric wins. A hat needs a brim of at least 7.5 centimetres all the way round; a baseball cap leaves the ears and neck, where my mother's cancers clustered, fully exposed.
- Sunglasses marked UV400 or 100 percent UV protection, because ocular melanoma and eyelid basal cells are real.
- Sunscreen on whatever is still showing.
How to check your own skin: ABCDE and the ugly duckling
Around half of melanomas are first noticed by the patient or a partner, not a doctor (Brady et al., Cancer 2000). Melanomas found by patients are, on average, thicker than those found at a skin check, which is why the point of self checking is not to diagnose but to shorten the delay. Once a month, in good light, with a hand mirror and a phone camera:
- Face, ears, scalp (use a hair dryer to part the hair), neck.
- Front and back of the torso, both sides with arms raised.
- Arms, armpits, both sides of the hands, between the fingers, under the nails.
- Legs, back of the legs, feet, soles, between the toes, under the toenails.
- Buttocks and genitals. Nobody enjoys this bit. Melanoma does not care.
Photograph anything you are unsure of next to a ruler or a coin, and photograph it again in a month. Non melanoma skin cancers look different: a basal cell is often a pearly, shiny bump or a sore that heals and reopens; a squamous cell is a firm, scaly, crusted lump that may be tender. Any sore that has not healed in four weeks is a sore that needs a doctor.
Weight, diet and skin cancer: what the evidence actually supports
This is not a sun cancer article that pretends food will save you. It will not. But two things about body weight and diet are worth knowing. First, a meta analysis of 21 studies found men with obesity had about 31 percent higher melanoma risk, with a weaker and less consistent link in women (Sergentanis et al., European Journal of Cancer 2013). Higher BMI is also associated with thicker melanomas at diagnosis, partly because larger bodies have more skin to check and more of it is hard to see. If you want to know where you stand, our BMI calculator shows both the standard and the lower Asian and Black thresholds and links to what to do about the number. And if you are carrying extra weight, the three obesity articles on this site are written without judgement.
Second, one nutrient has trial evidence. Nicotinamide, a form of vitamin B3, taken as 500 mg twice a day for a year cut new non melanoma skin cancers by 23 percent in 386 Australians who had already had at least two (Chen et al., NEJM 2015, ONTRAC trial). The effect disappeared when they stopped taking it. It is cheap, over the counter and worth discussing with a dermatologist if you are in the "already had one" group, which includes my mother, who now takes it. It is not niacin (which flushes) and it has no proven effect on melanoma. The full food and supplement picture, including omega 3, carotenoids and green tea, is covered in our skin cancer diet and exercise guide.
The vitamin D question
People ask whether avoiding the sun will leave them deficient. In the Nambour trial, daily sunscreen users had the same vitamin D levels as the control group after the trial, because nobody applies enough to block it completely and because the amount of sun needed is small (Marks et al., Archives of Dermatology 1995). For fair skin at mid latitude, ten to fifteen minutes of forearm sun a few times a week in summer is plenty. In winter above roughly 40 degrees north (London, Chicago, Toronto), the sun is too weak to make any vitamin D between October and March regardless of what you do, which is why the UK government advises everyone to take 10 micrograms (400 IU) a day through the winter (NHS). Take the tablet. Keep the hat.
A realistic prevention plan
| Habit | Evidence | What it costs you |
|---|---|---|
| Sunscreen every morning, April to September (or all year in sunny climates) | Halved melanoma in the only randomised trial | Ninety seconds |
| Never use a sunbed | 75 percent higher melanoma risk if started under 35 | Nothing |
| Shade and long sleeves between 10 and 4 on high UV days | Removes 60 percent of daily UV exposure | A rash vest and a proper hat |
| No sunburn for the children, ever | Each blistering burn before 20 adds risk for life | Vigilance on holiday |
| Monthly self check, photograph anything odd | Half of melanomas are found by patients | Ten minutes |
| Yearly professional check if you have any red bars on the risk chart | Thinner melanomas at diagnosis | One appointment |
| Keep weight in the healthy range, eat the Mediterranean way | Modest reduction in melanoma risk, large reduction in everything else | Ongoing, but you were going to anyway |
My mother's eleven scars came from a childhood nobody could have protected her from, because nobody knew. My children do not have that excuse, and neither do I. If you take one thing from this article, take the Nambour result: the difference between the people who got melanoma and the people who did not was not a lifestyle overhaul. It was a small tube of cream, every morning, without thinking about it.
Read next
- Is skin cancer curable? Treatment and survival by type and stage
- Skin cancer diet and exercise: foods to eat, foods to limit, and how to move safely
- BMI calculator with Asian and Black thresholds
- Kidney cancer symptoms, causes and how to lower your risk
Frequently asked questions
What is the best way to prevent skin cancer?
Avoid sunburn and sunbeds entirely, stay in shade or covered between 10am and 4pm on high UV days, and apply broad spectrum SPF 30 or higher every morning from spring to autumn. Daily sunscreen halved melanoma in the Nambour randomised trial.
Can skin cancer be prevented completely?
Not completely, because genetics, past exposure and some rare causes play a part, but around 86 percent of melanomas and 90 percent of non melanoma skin cancers are attributed to UV exposure, which is largely controllable.
How often should I check my skin?
Once a month, head to toe, including the scalp, soles, nails and between the toes. Photograph anything you are unsure of and compare after four weeks. See a doctor about any new, changing or non healing spot.
Does diet prevent skin cancer?
Diet cannot replace sun protection. Nicotinamide 500 mg twice daily reduced new non melanoma skin cancers by 23 percent in people who had already had them. A Mediterranean pattern, a healthy weight and limited alcohol are associated with modestly lower risk.
Is a tan safe if I never burn?
No. A tan is the skin's response to DNA damage that has already happened. There is no such thing as a healthy tan, and a base tan offers protection of roughly SPF 3.
This article is for general information and does not replace individual medical advice. If you have a new, changing or non healing skin lesion, see your GP or a dermatologist.
