It is swim season and the lifeguards at the local pool are working hard and hopefully protecting themselves against the harmful effects of ultraviolet A (UVA) and ultraviolet B (UVB). Some of the guards are wearing zinc oxide on their noses. They are easy to spot. Zinc oxide is a physical sun block. Nurses and patients should not underestimate its effectiveness.

Physical sunscreens, most often referred to as sunblocks, are products containing ingredients such a titanium dioxide and zinc oxide, which physically block ultraviolet radiation. These agents provide broad protection against both UVB and UVA. They can be cosmetically unacceptable to many people because they are often messy, visible, and do not easily wash off. However, some new zinc oxide products are available in brightly colored preparations which appeal to some. The amount of sun protection these agents provide, while potentially high, cannot be quantified in the same manner as sunscreen sun protection factors.

Physical sun blocks come in two types: zinc oxide and titanium dioxide, which are natural minerals. The benefit of physical blockers is that they don't decompose through sun exposure, so they theoretically last longer than chemical sunscreens. These agents work by sitting on the skin’s surface, and because titanium dioxide and zinc oxide are inorganic compounds, they are not absorbed into the skin. Light is either absorbed into sunblock material or reflected away from the skin, similar to a mirror or aluminum foil. In addition to being nonirritating and nonallergenic, these agents do not produce or aggravate acne. Zinc oxide has a long history of safe use. It is not irritating and compatible with sensitive skin. In fact, zinc oxide is a skin protectant and anti-irritant, and is widely used in treating various forms of dermatitis and skin irritation, including diaper rash.

The main complaint about zinc oxide-based blocks is that they may leave unsightly white residue. In fact, the concentrations of ordinary forms of zinc oxide required for a high degree of protection against the full range of UVA and UVB inevitably produce some whitish tint. Because the thick zinc oxide paste can create a white film on the skin that is unacceptable to many, some sunscreens contain micronized zinc oxide sun block that is transparent when applied. More research is being done to develop sunblocks with zinc oxide and titanium dioxide that are more cosmetically acceptable. Zinc oxide or titanium dioxide is also a safe choice for young children

Do not underestimate the effectiveness of zinc oxide. It is a great sunblock and provides protection against UVA and UVB. As research continues, hopefully there will be more and more sunblocks with zinc oxide that are cosmetically acceptable beyond the pool.