Sunscreen 101

June 13, 2023 Rachel Marlowe

Summer is officially here and that means it's time to re-up your supply of sunscreen. We assume that by now sunscreen is already a part of your daily skincare routine but, if it’s not, here's a reminder as to why it should be and how to choose the right sunscreen.

What is Sunscreen?

Sunscreen is a topical product that helps protect against sun damage by either absorbing or reflecting ultraviolet radiation. Ultraviolet (UV) radiation is a type of energy produced by the sun and is made up of two types of rays: UVA and UVB. While exposure to sunlight has multiple benefits, including enabling your body to make vitamin D, which strengthens your bones and regulates your immune system, it also increases your risk of skin cancer, and it’s estimated that about 80% of skin’s aging is caused by sun exposure. Wearing sunscreen is therefore the best–and easiest–way to protect your skin.

What is SPF?

SPF stands for “sun protection factor” and the number beside it indicates how well the sunscreen protects skin against sunburn. SPF is not an indicator of how long you can stay out in the sun, but how much longer it takes to produce sunburn on SPF protected skin versus unprotected skin. As the SPF value increases, the sunburn protection also increases so, for instance, if you’re wearing SPF 30 it would take you 30 times longer to burn than if you were not wearing any sunscreen.

No matter how high the SPF, UV radiation can always get through to the skin, however, so no sunscreen can ever completely prevent sunburn and the associated skin damage. Additionally, SPF is only a measure of how well the sunscreen protects skin against UVB radiation, not the deeper-penetrating UVA. To protect against both UVB and UVA radiation, you need a broad spectrum sunscreen. The Skin Cancer Foundation therefore recommends a water-resistant, broad-spectrum sunscreen with an SPF of 30 or higher for any extended outdoor activity.

SPF also needs to be applied properly to work effectively. The Skin Cancer Foundation recommends applying a quarter to a third of a teaspoon to your face and neck and two tablespoons to your body 30 minutes before going outside, and reapplication every two hours or immediately after swimming or sweating.

What are UVA and UVB Rays?

Ultraviolet light is invisible to humans, because it has shorter wavelengths than the light we can see. Within the UV spectrum, there are two types of rays, Ultraviolet A (UVA) and Ultraviolet B (UVB), each of which penetrates your skin differently.

UVB has a shorter wavelength and is associated with skin burning. UVA has a longer wavelength and is associated with skin aging. There are also two types of UVA rays: UVA1 and UVA2.

UVB penetrates and damages the outermost layers of skin. UVA rays, while slightly less intense than UVB, penetrate the skin more deeply.

UVB intensity fluctuates and is strongest late-morning to mid-afternoon and can damage your skin year-round, especially at high altitudes or on reflective surfaces like snow or ice. UVB rays can be filtered and do not penetrate glass.

UVA, meanwhile, accounts for up to 95 percent of the UV radiation reaching the earth and maintains the same level of strength during daylight hours throughout the year. UVA can also penetrate windows and cloud cover.

What are the Different Types of Sunscreen

First up, it’s important to remember that sunscreen can expire and when it does, it may leave you vulnerable to a sunburn, sun poisoning, or other skin damage. The Food and Drug Administration mandates that all sunscreens maintain their full strength for three years so check the expiration date on the bottle.

There are two types of sunscreens: chemical and physical. Chemical sunscreen absorbs UV rays, converts them into heat, and releases them from the body. Physical sunblock sits on top of the skin and reflects UV rays.

Chemical Sunscreen

Chemical sunscreens contain active ingredients such as Avobenzone, Homosalate, Octinoxate, and Oxybenzone. Chemical sunscreens are usually easily absorbed by the skin and are often clear, making them more wearable, however they also wear off more quickly and need to be reapplied every couple of hours.

At Onda, we look to the Environmental Working Group's safety and ingredient standards to help inform our own. The organization reports that in 2021, the Food and Drug Administration, which governs sunscreen safety, proposed updates to sunscreen regulations, having found that only two ingredients (Zinc Oxide and Titanium Dioxide) are safe and effective, based on information currently available. Twelve other ingredients, including the most popular ones found in chemical SPFs like Avobenzone, Homosalate, and Oxybenzone, were not generally recognized as safe and effective due to insufficient data. Additionally, the EWG recommends consumers avoid sunscreens with Oxybenzone after studies supported the FDA’s finding that it can cause allergic skin reactions, act as an endocrine disruptor, and increase the risk of breast cancer and endometriosis.

You have also no doubt heard that certain chemical sunscreens have proven to be damaging to coral reefs. In 2021, Hawaii in fact banned sunscreens containing Oxybenzone and Octinoxate because studies indicated these chemicals were having a harmful impact on the marine environment and ecosystems. The potential harm to both our bodies and the environment combined have therefore informed Onda's decision to favor mineral sunscreens. Because “innovation” is one of our brand pillars and we endeavor to keep abreast of all that is new in the ever-evolving landscape of beauty technology, we will continue to follow safety data and innovations in chemical formulations.

Physical Sunscreen

Physical sunscreens, also called mineral sunscreens, are primarily composed of Zinc Oxide and Titanium Dioxide, both of which are classified as safe and effective by the FDA. Zinc Oxide is able to protect against the entire UVA range and some UVB. Titanium Dioxide is able to protect against UVA2 only and UVB. While long-lasting, physical sunscreens tend to be heavier and sometimes leave a white cast on the skin, although modern sunscreens are often formulated with nano Zinc Oxide, whose smaller particle size does not leave a white cast, and clear Zinc Oxide.

Aside from offering safe, broad SPF, physical sunscreens containing Zinc Oxide have several other benefits. Zinc Oxide has anti-inflammatory properties, making it ideal for those with sensitive skin and skin conditions such as eczema and rosacea. For those prone to melasma or hyperpigmentation—both conditions that can be triggered or worsened by the heat and light of the sun’s rays–unlike chemical sunscreens which work by absorbing into the skin where they convert the UV rays into heat, then release that heat from the skin, physical sunscreens block UV light from penetrating the skin without producing heat.

How To Choose A Sunscreen

The American Academy of Dermatology recommends the following when choosing a sunscreen:

Make sure the label says “broad spectrum”. The words broad spectrum mean that the sunscreen will protect your skin from both UVA and UVB rays.

Use an SPF 30 or higher, which can block about 97 percent of UVB rays.

Look for the words “water resistant”. This means that the sunscreen will stay on wet or sweaty skin for a while before you need to reapply. Water resistance lasts either 40 or 80 minutes.