Sunscreen sticks, a solid, portable formula in a twist-up tube, have surged in popularity due to their convenience and mess-free application. Like any sun protection product, their effectiveness hinges entirely on correct usage. The primary concern is not the formula’s ability to protect against ultraviolet (UV) radiation, but rather the user’s ability to apply a thick enough and uniform layer to the skin. To achieve the labeled Sun Protection Factor (SPF), a specific amount of product must be deposited, which is often difficult to gauge with a solid stick.
The Science of Sunscreen Sticks
The unique, solid nature of a stick sunscreen is achieved through a specific formulation that differs greatly from liquid lotions. Sticks primarily rely on a base of waxes and emollients to maintain their compact structure and allow for smooth gliding across the skin. These waxes provide the necessary mechanical stability to prevent the stick from breaking during application or melting in heat.
These solidifying agents, like petrolatum and various oils, allow the UV filters to be suspended in a firm matrix. Active sun-blocking ingredients are either organic (chemical) filters (e.g., avobenzone) or inorganic (physical) filters (e.g., zinc oxide and titanium dioxide). Both types of filters work by absorbing or reflecting UV rays, and most high-quality sticks contain the same protective ingredients as their liquid counterparts.
Achieving Full Coverage: The Application Technique
The effectiveness of any sunscreen is tied directly to the amount applied, which is scientifically standardized at 2 milligrams of product per square centimeter of skin (2 mg/cm²). This density is used in a laboratory setting to determine the product’s labeled SPF. For a stick sunscreen, achieving this necessary thickness is the most common challenge and the main reason for user error.
Simply swiping the stick once or twice across an area will not deposit the required amount of product for full protection. Studies show that a single stroke fails to create a uniform protective film, resulting in SPF figures significantly lower than the label suggests. To ensure adequate coverage, dermatologists recommend applying at least four passes of the stick back and forth over each area of skin.
This multi-pass technique is necessary because the stick’s waxy nature makes it difficult to transfer a large volume of product in a single go. After applying the multiple layers, gently rub the area with your fingers to ensure the product is evenly distributed and to fill in any microscopic gaps. The goal is to create a visible, uniform film on the skin’s surface, which indicates a sufficient amount of product has been deposited. Failing to rub the stick in compromises the overall SPF by leaving microscopic areas of exposed skin.
The application pressure also plays a role in the final film thickness and uniformity, requiring firm, even pressure throughout the process. For the face, achieving the required 2 mg/cm² may take more than four passes, especially with drier formulas; continue applying until the area is visibly coated. Reapplication is necessary, and the stick should be reapplied at least every two hours, or immediately after swimming or heavy sweating, just like any other sunscreen.
Practical Comparison: Sticks Versus Liquids
When comparing the stick format to traditional liquid lotions, the trade-offs are mainly about convenience versus ease of achieving full coverage. Sticks are valued for their portability and mess-free application, making them ideal for reapplication on the go or for use on children. They are spill-proof and compact, fitting easily into a pocket or small bag.
The stick form is excellent for targeted application on small or sensitive areas like the face, nose, ears, and around the eyes, where a lotion might run or be difficult to control. Many stick formulations are designed to be water-resistant, making them a practical choice for athletes or individuals who sweat a lot, as they are less likely to drip into the eyes.
However, the solid form presents a disadvantage when attempting to cover large areas of the body, such as the back or legs. Spreading a liquid lotion over a broad surface is faster and makes it easier to visually confirm uniform coverage. Using a stick on a large area is time-consuming and risks leaving an uneven layer or missed spots, even with the correct multi-pass technique. Therefore, the stick is best used as a supplement to a liquid sunscreen, perfect for touch-ups and small, high-exposure areas, while a lotion or spray is preferred for initial full-body coverage.