There's no one ingredient in sunscreens that protects you from the damaging rays of the sun, the Mayo Clinic says. One of the most efficient ways of shielding your skin from sunburn and signs of premature aging is choosing a sunscreen that offers broad-spectrum protection against both ultraviolet A and B rays. Zinc oxide is one ingredient you might want to look for on your product's label, as it shields you from both UVA and UVB rays.
Types of Suncreen
The active ingredients in your sunscreen fall under one of two categories, organic and inorganic, the latter of which encompasses zinc oxide, correspondent Marc Reisch says in a June 2002 report in "Chemical & Engineering News." Inorganic sunscreens either contain zinc oxide, or another inorganic substance, titanium dioxide. Inorganic sunscreens offer protection from UVA rays, which the American Osteopathic College of Dermatology describes as "tanning rays," but also UVB rays, which cause sunburn. Organic sunscreens contain other types of active ingredients, such as octyl methoxycinnamate, avobenzone and oxybenzone, Reish says. These products work slightly differently from those that contain zinc oxide.
How Zinc Oxide Works
A simpler explanation for how zinc oxide works is that it provides a thin layer between your skin and the sun, says the Mayo Clinic, which defines products containing zinc oxide as physical sunscreens. Zinc oxide-based sunscreens reflect and scatter the sun's rays, while chemical sunscreens absorb UV rays before they reach your skin.
Zinc oxide may bring to mind an obvious layer of white on your nose and cheeks, but in fact, zinc oxide is the ingredient used in dense diaper rash creams that act as a barrier between an infant's skin and a diaper. However, in May 2008, the American Academy of Dermatology noted that new grinding technologies have made particles in zinc oxide even finer, resulting in sunscreens that look transparent on your skin. This also enhances the ease of application and the product's evenness on the skin and makes it "cosmetically acceptable."
Other Benefits of Zinc Oxide
Some of the chemicals in sunscreens may be problematic for people with sensitive skin. Dr. Andrew Weil notes that oxybenzone and para-aminobenzoic acid, which is not used too much in sunscreens, are two such ingredients associated with skin irritation. Weil recommends selecting sunscreens with zinc oxide or titanium dioxide for gentle and thorough sun protection.
Using Your Sunscreen
Whichever type of sunscreen you choose, select one with a sun protection factor of at least 30 that bears the American Academy of Dermatology Seal of Acceptance, the AAD advises. Apply it generously to all parts of your body exposed to UV rays at least 30 minutes before you head outdoors and reapply it in two-hour intervals or whenever you sweat a lot, get out of the pool or rub off with a towel. Harmful UV rays can penetrate cloud cover, so make sure to wear sunscreen on overcast days.