Zinc oxide has been used as a dermato-therapeutic agent for over 300 years, first as a component of calamine and then on its own in various preparations.

In the "Pharmacopea Londinensis" published in 1618 for the London College of Physicians, Lapis Calaminaris is mentioned as a component in three of 42 therapeutic ointments. In the U.S. Dispensary of 1883, calamine is mentioned and recommended for use as "a mild astringent and exsiccate in excoriations and ulcerations."

Calamine was originally a naturally occurring mixture of zinc containing compounds which was used as is or heated and pulverized into a powder which was then applied to the skin. What we know as calamine today is actually "neo-calamine", a mixture of zinc oxide and iron oxides. This mixture was standardized in 1947 with the publication of the recipe in that year's National Formulary in the United States.

Today, zinc oxide is still widely used as a topical therapeutic medication. In fact, it may well be the most commonly used topically applied drug of all time. One of the more important uses for zinc oxide is as a sunscreen. Why is zinc oxide ideally suited for this purpose?

Since the late 1920s, sunscreens have been used by people to protect themselves from the harmful effects of the sun. The original sunscreens were organic molecules that worked by absorbing the sun's radiation. Para-Amino Benzoic Acid (PABA), perhaps the best known sunscreen, was patented in 1943 and enjoyed a long period of common usage. It has since fallen out of favor but other organic sunscreens still make up the vast majority of the chemicals used for this purpose.

In addition to the organic sunscreens, there are also several inorganic chemicals used to block the sun. Some common ones are zinc oxide, titanium dioxide and iron oxide. The inorganic chemicals offer good protection and, unlike their organic counterparts, are not absorbed into the skin. Because of this, they do not cause any adverse reactions such as allergies and are thought to be generally safer. Among these, zinc oxide has an unmatched history of safe and effective long-term use.

Zinc oxide has been used for centuries to protect and heal the skin. When it was first intentionally used as a sunblock is not clear but, at least during this century, it has been considered common knowledge that zinc oxide is the most effective sunblock available. Everyone can recall lifeguards and tennis players with zinc oxide on their lips and noses. The military even issued zinc oxide paste to pilots during both World Wars to use in case they were downed and excessively subjected to the elements.

UVB causes sunburn and UVA causes skin aging and skin darkening (tanning). Both UVA and UVB are involved in skin cancer. Given this knowledge, any consumer product claiming sun protection needs to block both UVA and UVB. To do anything else is doing a disservice to the public. Recall that a sunscreen that blocks only UVB will still prevent a sunburn.

Sunburn is the body's built in alarm system that tells us when we have had too much UVR. When this response is "bypassed" people stay out longer than they normally would and, if using only a UVB block, expose themselves to unnaturally high doses of UVA radiation. This is one of several proposed explanations for the rising incidence of skin cancer. Fortunately, zinc oxide blocks virtually the entire UVA and UVB spectrum. This makes it the most complete block known.