Zinc Oxide Uses: Medicinal Creams, Calamine Lotion, and Sunscreen
Zinc Oxide and Its Uses
Zinc oxide is a white powder that has been used in medicinal creams and as a skin decoration since ancient times. It forms a coating on the skin, which acts as a barrier that protects skin problems from further damage. These problems include irritations, abrasions, and rashes. Zinc oxide also reduces itching and is mildly antibacterial. In addition, it's an astringent (a substance that shrinks tissues and can help reduce the size of a swelling). It's the main component of calamine lotion.
Zinc oxide has yet another useful ability. It blocks dangerous ultraviolet radiation from the sun, so it’s useful in sunscreens. Its particles are often reduced to nanoparticle size for sunscreen use in order to reduce the white coating on the skin. The chemical is also used as a food additive and in supplements to provide us with zinc, an important nutrient for our bodies.
This article discusses some common uses of zinc oxide. Anyone with serious medical symptoms or with ones that aren't helped by zinc oxide should visit a doctor.
Diaper Rash Treatment
Diaper rash is a common baby ailment. As its name suggests, it can develop anywhere on a baby's body that is covered by a diaper. Friction caused by a wet diaper rubbing over the skin can cause the rash. In addition, chemicals from urine, feces, and detergents can irritate a baby's delicate skin and cause a rash. It's also possible for a baby to develop a rash due to an allergic reaction to something that touches the skin.
Zinc oxide (ZnO) creams or ointments can often be helpful in relieving a baby's discomfort. A cream and an ointment are very similar. An ointment contains a larger proportion of oil than a cream, however. The products are produced in different concentrations and usually contain either 15% or 40% ZnO. They may include petroleum jelly as well as zinc oxide and are available over the counter in pharmacies.
A pharmacist or doctor can help someone choose the best cream or ointment for a particular situation. Both products are used to prevent and treat diaper rash. Lower concentrations of ZnO are present in prevention products and higher concentrations are present in treatment ones.
Zinc oxide allergies are rare, but they do occur. If a zinc oxide cream increases itchiness and makes a rash worse, it shouldn't be used. A doctor or pharmacist should be consulted to find an alternate treatment for the problem.
Although friction and irritation cause most cases of diaper rash, some cases are caused by a yeast or bacterial infection. A doctor must prescribe a treatment for these infections. It's generally recommended that a baby sees a doctor if a diaper rash doesn't disappear within four days, if it appears to be getting worse, or if it's accompanied by other symptoms such as oozing, bleeding, or a fever.
Zinc oxide creams and ointments are also used to help relieve the discomfort of hemorrhoids. These are areas in the rectum or around the anus where veins are swollen due to increased pressure. Hemorrhoids are painful and itchy and may bleed. They are sometimes known as piles.
Hemorrhoids may be completely internal and invisible when they're in the rectum (the last part of the large intestine where feces is stored before being eliminated from the body), or they may be external and visible. Sometimes internal hemoorrhoids become so large that they protrude through the anus and are said to be prolapsed.
Many people report that a zinc oxide product reduces the pain and itching of hemorrhoids. The product also acts as a protective barrier and can prevent further injury.
Bleeding from the anus must be checked by a doctor to make sure that it's caused by a hemorrhoid and not by something more serious.
Calamine lotion is part of many first aid kits. It's a liquid that's used as a topical (skin) application to ease the pain of stings produced by stinging nettles, poison ivy, poison oak, and poison sumac. In addition, it's classified as an antipruritic (a substance that stops itching) and relieves the itchiness of sunburns and dermatitis. The lotion mustn't be taken internally.
La Calamine is the French name for a city in Belgium, which is also known as Kelmis. The area contains a former zinc mine, from which an ore named calamine was extracted. We now know that the ore consists of two different minerals: zinc carbonate, which is also known as smithsonite, and zinc silicate, which is also called hemimorphite. The term "calamine" is still used, however, even though it isn't a very specific term and could refer to either zinc mineral.
Today's calamine lotion contains zinc oxide and iron oxide mixed with water and is pink in color. The brand that I buy contains no artificial color. The lotion is pink because it contains iron oxide, which is red in its pure form. Some lotions also list calamine as an ingredient.
Calamine lotion isn't a solution but is actually a suspension of zinc oxide in water. ZnO doesn't dissolve in water. The liquid has to be shaken before use to suspend the ZnO particles that have settled on the bottom of the container.
If your condition gets worse or if it does not improve within 7 days, or if rash or irritation develops, stop using calamine and check with your doctor.— Mayo Clinic
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Zinc oxide is a natural chemical that is found in the Earth's crust. It's also produced synthetically.
Zinc Oxide in Sunscreens
Dermatologists say that we should wear sunscreen in order to prevent sunburn and reduce the risk of skin cancer and premature skin aging. Although there are several effective sunscreen ingredients, some of them can be absorbed into our bodies through our skin, where they may cause problems.
Zinc oxide seems to be the best sunscreen ingredient because it combines effectiveness with safety. It isn't absorbed through the skin and is considered to be a safe substance. The chemical scatters ultraviolet rays coming from the sun and absorbs and reacts with only a small percentage of them. (Reactions involving radiation can produce dangerous products.)
Zinc oxide is a broad spectrum sunscreen, meaning it blocks both UVA rays and UVB rays. UVA rays have a longer wavelength and penetrate deeper into the skin than UVB rays, which have a shorter wavelength. Both types of ultraviolet radiation are dangerous.
Unfortunately there is one major disadvantage to a zinc oxide sunscreen which probably dissuades many people from using it: it gives the skin a pasty white appearance and is very visible.
Nanoparticles in Sunscreens
A solution to the problematic skin appearance produced by zinc oxide is to turn the chemical into nanoparticles, which almost eliminates the white color. Nanoparticles are those particles that have a diameter from 1 to 100 nm (nanometers). One nanometer is a billionth of a meter.
Nanoparticles in sunscreens don't appear to penetrate our bodies beyond the outer layer of skin. This layer is called the stratum corneum and is made of dead cells. However, the claim that nanoparticles on the skin never enter the body is somewhat controversial because not all skin is healthy. The skin's barrier function may be damaged in sunburned areas or in areas injured by insect bites and stings, shaving cuts, and other wounds. This damage may allow nanoparticles to pass through the skin.
Some people are concerned about nanoparticles entering the body because a chemical's properties and behavior often change when its particles are reduced to a nano size. The chemical's behavior may be safe and predictable when it's in its normal form but unsafe and unpredictable when it's in its nano form. The evidence obtained so far indicates that zinc oxide nanoparticles on the skin are likely safe, however.
Zinc Oxide Nanoparticles
At the moment, zinc oxide seems to be the best sunscreen (in my opinion) even when it exists as nanoparticles. The version that I use gives a slightly white tinge to my skin even though it contains zinc oxide in nanoparticle form. I like the other ingredients in the sunscreen and find it to be effective at preventing sunburn, however, so I continue to use it.
Sunscreen manufacturers often coat the zinc oxide nanoparticles to make them less reactive with sunlight, causing fewer potentially dangerous free radicals to form. Free radicals can damage DNA. Even if these free radicals do form, however, the evidence obtained so far suggests that they can't penetrate into the living area of healthy skin. Hopefully further research will clarify whether nanoparticles can pass through damaged skin, and if so, what we can do to protect ourselves.
Are you concerned about sunscreen safety?
A Versatile Chemical
Zinc oxide is a useful substance that also has a high degree of safety, with the possible exception of zinc oxide nanoparticles. It's been used as a skin treatment for many years and even today is sold in pharmacies to help treat skin problems and maintain health. It's a versatile chemical. A zinc oxide cream or lotion is a very helpful substance to keep in the home.
Questions & Answers
How does zinc oxide, both nano and non-nano forms, work in sunscreen?
In its usual form, zinc oxide scatters ultraviolet and visible light. Scattering is a process in which a particle absorbs electromagnetic radiation, including light, and then emits it without undergoing a chemical reaction. Scattering is not the same as reflection. In reflection, light bounces off an object without being absorbed. Zinc oxide does reflect light in addition to scattering it, however.
Zinc oxide acts as a barrier to dangerous UV radiation because it sends it back into the atmosphere by scattering and reflection instead of allowing it to enter the skin. It’s considered to be a physical sunblock instead of one that reacts chemically after light exposure.
Since zinc oxide reflects light so well, it often produces a white appearance on the skin. Reducing the ZnO particles to nanoparticle size reduces the reflection but doesn’t stop the scattering of UV light, so the substance continues to act as a sunscreen. Additional processes may occur due to the unusually small size of the particles, however. They may be photoreactive, which means that they may participate in chemical reactions after light exposure. Manufacturers generally coat the nanoparticles in sunscreen to reduce this possibility.
Research into the effects of zinc oxide nanoparticles is continuing. They are generally considered to be safe, but some questions have been raised about their safety in particular situations.
© 2012 Linda Crampton