For years, the conventional wisdom was that you should always slather on sunscreen before heading outdoors in the summer. However, growing awareness of toxic chemicals and hidden dangers in items we previously took for granted has made a lot of people question whether sunscreen is really as safe as the manufacturers claim. Whether you're doing your research before a big beach vacation or just worrying about everyday wear, it's important to stay safe, both from sun damage and potential sunscreen damage.

Types of Sunscreen

There are two main types of sunscreen. Physical blockers or non-chemical sunscreens work by simply reflecting the sun's rays. These always contain either zinc oxide or titanium oxide and often have a thick, heavy white color to them that doesn't absorb easily into the skin.

Chemical blockers absorb the sun's rays to keep them from penetrating your skin. Many different ingredients can go into these, including avobenzone, oxybenzone, octisalate, and others.

Bottle of sunscreen on beach georgeclerk / Getty Images


How is it Regulated?

In the United States, sunscreen is considered an over-the-counter drug and thus is regulated by the U.S. Food and Drug Administration (FDA). This means manufacturers must provide certain safety data about the ingredients, which the FDA can approve or deny. All sunscreens manufactured or sold by U.S. retailers are required to meet these safety standards. However, sunscreen that comes from overseas retailers may not be similarly regulated, so consumers should use caution when ordering foreign sunscreens online.

Multiple sunblock and oil bottles Grassetto / Getty Images


The Oxybenzone Concern

One of the main concerns raised about modern sunscreens is the presence of oxybenzone. This is a common ingredient in many formulas that use chemical blockers, and some studies show that it may act as a hormone disruptor in rats. However, Dr. Jennifer Lin of Harvard Medical School estimates that it would take approximately 277 years of sunscreen use for a human to reach the same levels of oxybenzone that have been shown to cause problems for rats. Another concern is that oxybenzone in sunscreen may be damaging to coral reefs when it washes off of swimmers' bodies. There is more evidence backing up this concern, and some regions on the ocean, such as Hawaii, are banning the ingredient.

Woman smiling with sunscreen sun PeopleImages / Getty Images


Skin Absorption

Another worry many people have is that sunscreen may pass through the skin and enter the bloodstream. However, researchers have found that sunscreen only penetrates the top layers of skin and does not appear to be absorbed deeper into the body. Aerosol sunscreens do present a related risk, however, which is inhalation. The small amounts inhaled during typical application do not appear to be harmful, but experts suggest applying spray sunscreen in a well-ventilated area and spraying it into the hand first before applying to the face and neck.

Woman sprays aerosol sunscreen sunblock RuslanDashinsky / Getty Images


The Skin Cancer Conundrum

Another commonly cited concern is that sunscreen may reduce the risk of more benign skin cancers while increasing the risk of melanoma, a deadly form of skin cancer; others worry sunscreen may increase the risk of all skin cancers. A few studies came to these conclusions, but they are small and have methodological problems. For example, some fail to account for the fact that regular sunscreen users tend to be in the sun more in general, which increases their skin cancer risk no matter what other factors may be at play. The majority of studies show that sunscreen reduces the risk of all types of skin cancer, including melanoma.

Dermatologist looking for skin cancer kali9 / Getty Images


Allergies and Sensitivities

One significant risk of sunscreen use is the potential for allergic reactions or skin irritation. This is more common with sunscreens that use chemical blockers, particularly oxybenzone, than physical ones, so some dermatologists recommend that people with sensitive skin only use physical blockers. People with a sensitivity to sunscreen can still find formulas that do not cause reactions.

Child with skin allergy hives Lizalica / Getty Images


Vitamin D Deficiencies

Vitamin D deficiency is a real problem that can be caused or exacerbated by a lack of sun exposure, and sunscreens do block the type of UVB rays our bodies use to create the nutrient. However, it typically only takes ten to 15 minutes of sun exposure a day to create enough vitamin D, so most people get plenty of it even while using sunscreen. People whose bodies don't make enough can also get it through dietary sources or supplements, so most experts still recommend using sunscreen.

Man smiling in sunlight electravk / Getty Images


How Effective is Sunscreen?

The general medical consensus is that commercially available broad-spectrum sunscreens are safe and highly effective at preventing all types of skin cancer when used correctly. Regular sunscreen use also significantly slows signs of premature aging, such as wrinkles and spots. Homemade formulas are also growing in popularity, but experts often recommend avoiding those, as most do not contain enough physical or chemical blockers to adequately protect the skin.

Woman applying sunscreen to baby ArtMarie / Getty Images


Other Ways to Protect Yourself

The best way to stay safe in the sun is to employ various strategies. Sunscreen use is key, but experts also recommend avoiding sun exposure whenever possible. Broad-brimmed hats and UV-resistant clothing are useful tools, as is staying indoors or in the shade as much as possible. The sun is particularly harsh between the hours of 10 a.m. and 4 p.m., so it is best to plan outdoor activities for the early morning or evening.

Woman with wide-brimmed hat sunny day andresr / Getty Images


How to Use Sunscreen

Even though most people have been using sunscreen their entire lives, experts say most are doing it wrong. The most common problem is a failure to reapply frequently enough. People should reapply sunscreen at least every two hours; it may need to be reapplied as often as every 30 to 40 minutes when swimming or sweating heavily. Most people also do not use enough of it. Adults should typically use about the amount that would fill a shot glass on their bodies, along with about a teaspoon on their faces.

Young girl applying sunscreen to nose ArtMarie / Getty Images


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