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By Sue Smith

Grillo Health Information Center

Q: Can you tell me what is important to look for when choosing a sunscreen?

A: Two types of sun rays are known to affect human health: ultraviolet A and ultraviolet B. UVA rays penetrate to the deep layers of the skin and cause sun damage such as wrinkles and age spots. UVB rays affect superficial layers of the skin and cause sunburns. More importantly, too much exposure to either type can lead to skin cancer, which is why sunscreens are an important part of cancer prevention.

First, look for a sunscreen that protects against UVA and UVB rays. This is called “broad spectrum” or “full spectrum” sunscreen.

The acronym SPF appears on most sunscreen labels. This stands for “sun protection factor” and indicates the extent to which the product protects the skin from UVB rays. Dermatologists recommend using a product with a minimum SPF of 30, but most agree that anything over SPF 50 provides only an incremental increase in protection and may not be worth the added expense.

While no sunscreen is waterproof, some are labelled “water-resistant” and are recommended for everyday use because they tend to stay on your skin longer.  But even water-resistant products need to be reapplied after swimming or sweating.

There are two main categories of sunscreens: mineral and chemical. The mineral type provides a physical barrier that blocks UVA/UVB rays before they penetrate your skin. Mineral type sunscreens contain zinc oxide and/or titanium dioxide. These have the advantage of being hypoallergenic but can be thick and messy to apply and may remain visible on your skin.

The chemical type of sunscreen consists of a variety of substances that absorb UVA/UVB rays and render them harmless by way of a chemical reaction. In the U.S., the active ingredients in this type of sunscreen include one or more of the following: avobenzone, ensulizole, homosalate, octinoxate, octisalate, octocrylene and oxybenzone. Chemical sunscreens tend to be easier than the mineral types to apply but may cause irritation to sensitive skin. Of note: the FDA is currently updating its regulations regarding the safety and effectiveness of all chemical sunscreen ingredients. More information can be found on the FDA website at

No matter which sunscreen you choose, it should be used every time you are outdoors and must be applied liberally and reapplied every two hours to be fully effective. Furthermore, even while using sunscreen, it is prudent to take other measures to protect yourself from the sun as much as possible. Avoid the sun’s strongest rays (10 a.m. to 2 p.m.), wear a hat and sunglasses, and put on long sleeves and pants when feasible.

Sue Smith volunteers with the Grillo Center, which offers free, confidential research to assist in health understanding and decisions. To use this service, contact or 303-415-7293. No research or assistance should be interpreted as medical advice. We encourage informed consultation with a health practitioner.

Where to find it

American Academy of Dermatology (AAD)

Google: AAD sunscreen faqs

Mayo Clinic

Google: mayo clinic sunscreen

Skin Cancer Foundation

Google: skin cancer foundation all about sunscreen

American Society of Clinical Oncology (ASCO)

Google: asco answers sunscreen ingredients