Myth: you do not need sunscreen on cloudy days
UV rays are not the same as visible light or heat. A substantial share of UV can pass through thin or broken cloud, and on some days it can feel cool and still be significant. Thick, heavy cloud reduces UV more, but it is hard to judge by eye how much. A common approach is to follow the UV index forecast in your area, which many weather services publish, rather than guessing from how bright or warm it feels.
Myth: darker skin does not need sunscreen
Melanin, the pigment that gives skin its color, offers some natural protection, and people with more melanin generally burn less easily. But that protection is partial, not complete. People of all skin tones can develop sun damage, uneven pigmentation and skin cancer, and in some cases problems are noticed later because they are less obvious. Sun can also darken marks left by blemishes, which is part of the story in the explanation of hyperpigmentation. Whether to use sunscreen daily is a personal choice, but the idea that anyone is entirely exempt is not accurate.
Myth: a higher SPF means you can stay out much longer
SPF 50 is not twice as protective as SPF 25 in a simple sense. The commonly cited figures are that SPF 15 filters about 93% of burning UVB, SPF 30 about 97% and SPF 50 about 98%. The step up in protection is real but small, and a higher number can lead people to stay out longer or skip reapplying. The details and limits are explained in the article on SPF numbers.
Myth: one application lasts all day
Sunscreen wears off through sweat, rubbing, water and time. Many guidelines suggest reapplying about every two hours of outdoor exposure, and sooner after swimming or toweling off. The reasons are covered in the piece on sunscreen reapplication. If you are mostly indoors, a morning application may be adequate for a short outdoor trip, but a long outdoor day is different.
Myth: makeup with SPF is enough
Foundations and powders with SPF can add some protection, but people tend to apply them far more thinly than sunscreen is tested at. To get the stated SPF from foundation, you would typically need a quantity that looks and feels heavy. For this reason, many people prefer wearing a dedicated sunscreen first and treating the makeup SPF as an extra, as discussed in the article on sunscreen under makeup.
Myth: a base tan protects you
A tan is a sign that skin has been exposed to UV and is responding to damage. Any natural protection from a tan is generally considered small, often compared to a low SPF. Deliberately tanning, indoors or outdoors, is not considered a safe way to prepare skin.
Myth: you cannot get sun exposure through windows
Window glass tends to block much of UVB but allows a good share of UVA through. Long periods beside a sunny window or driving may therefore add up over time. How strongly this affects you depends on the glass, your position and how long you are there. The two types of rays are compared in the article on broad spectrum protection.
Myth: sunscreen is toxic or does not work
Sunscreen ingredients are regulated and have been studied for a long time, although research and regulatory reviews continue, and some countries approve different filters. Some people prefer mineral formulas for personal reasons, and that is a reasonable choice, as explained in the article on mineral sunscreen. If you have specific concerns about an ingredient, a pharmacist or doctor can talk through them. Skipping sun protection altogether has its own well-established downsides.
Myth: sunscreen alone is enough
Sunscreen is helpful but imperfect, since it is often applied too thinly and wears off. Shade, hats and clothing offer protection that does not depend on how well you apply a product. Those options are covered in the article on protective clothing.
Myth: if you are not burning, you are not being damaged
Burning is one sign of too much UV, not the only one. Cumulative exposure can affect skin even without a burn, for example through gradual photoaging. If you notice a spot that is new, changing, bleeding or not healing, a qualified health professional should look at it. This article is general information, not medical advice.