Skin cancer is the most commonly diagnosed cancer in the United States, outpacing every other type combined. By age 70, at least 1 in 5 Americans will develop it. The primary driver is ultraviolet radiation from the sun, and the primary defense is sunscreen. The problem is that most people are applying it wrong, skipping it when they think they do not need it, or relying on products that offer far less protection than advertised.

A lot of that comes down to misinformation that has quietly settled into everyday habits. Here is what the evidence actually says.

The time of day and season matter more than most people realize

UV rays are strongest in North America between 10 a.m. and 4 p.m., and that window carries the highest risk of skin damage. But the hours outside that range are not safe by default, and neither are overcast days. Up to 90% of the sun’s rays can penetrate cloud cover, meaning a gray sky offers almost no meaningful protection. Water, sand and snow compound the problem by reflecting UV radiation back onto exposed skin from below.

Sun protection is a year-round daily habit, not a beach day precaution.

A tan is not a sign of health. It is a sign of damage.

The idea that tanning without burning means the skin is handling sun exposure well is one of the most persistent and damaging myths in skin care. A tan is the body’s response to DNA injury. The skin darkens because it has been damaged and is attempting to protect itself. That process does not prevent future damage, and there is no threshold of sun exposure that qualifies as safe. Even a light glow increases the risk of premature aging and skin cancer.

This applies regardless of natural skin tone. Darker skin contains more melanin, which slows the rate of burning, but it does not block UV radiation or eliminate the risk of sun damage, dark spots, wrinkles or skin cancer. Sunscreen is relevant for every skin tone.

Makeup with SPF is not a substitute for sunscreen

Foundation that includes SPF 30 or higher provides some sun protection, but it falls short of traditional sunscreen for two reasons. First, most people apply far less foundation than would be needed to achieve the labeled SPF level. Second, makeup is typically applied only to the face, leaving the neck, ears, chest and hands without protection.

Applying a layer of traditional sunscreen underneath foundation covers those gaps. Any area that will be exposed to sunlight warrants direct sunscreen application.

Higher SPF numbers offer diminishing returns

SPF 30 blocks approximately 97% of UVB rays. SPF 100 blocks only 1% to 2% more than that. The difference between a mid-range and a premium SPF product is smaller than most people assume, and no sunscreen blocks UV radiation completely.

More important than SPF number is how often the product is reapplied. Protection typically lasts no longer than two hours regardless of SPF rating, and it degrades faster when swimming or sweating. A broad-spectrum, water-resistant sunscreen with an SPF of at least 30, reapplied consistently throughout the day, outperforms a single application of SPF 100 left on for six hours.

Physical and chemical sunscreens work in fundamentally different ways

Physical sunscreens, also called mineral sunscreens, sit on the surface of the skin and deflect UV rays using active ingredients like zinc oxide or titanium dioxide. They are generally considered safer for sensitive skin, children and people with pigmentation concerns. Earlier versions left a visible white residue, but tinted and sheer formulations are now widely available.

Chemical sunscreens absorb UV rays into the skin and convert them to heat. They apply more easily and invisibly but can irritate eyes and trigger allergic reactions in some people. Products containing oxybenzone are worth avoiding when possible, as the ingredient has been associated with hormonal disruption and skin sensitivity.

Spray sunscreens of either type are significantly less effective than lotions applied by hand, since achieving even coverage with a spray is difficult in practice. Products marketed as sunscreen that contain only oils like coconut, olive or jojoba provide no measurable UV protection.

Vitamin D and sunscreen can coexist

Concern about blocking vitamin D production keeps some people from using sunscreen consistently. Even well-applied sunscreen allows 2% to 3% of UVB rays through, which is enough for the body to produce the vitamin D it needs. For anyone still concerned about their levels, diet and supplements offer a straightforward alternative that does not require trading skin health for it.

Expired sunscreen is not doing its job

The FDA requires sunscreens to maintain their original effectiveness for at least three years. Products that have passed their expiration date, or that have been stored in extreme heat or cold, may no longer perform as labeled. Anyone using sunscreen daily through outdoor seasons should be going through bottles fast enough that expiration is rarely a concern. If the bottle has been sitting in a bag since last summer, it is worth replacing.