Why do some skincare products pill?

Similar to flaky skin, pilling is characterized by the formation of small aggregates on the skin’s surface during the application of skincare products. For a long time, this phenomenon was based mainly on empirical observation, until the publication in 2024 of the first clinical study dedicated to it, conducted by LIU S. et al. in the journal Skin Research and Technology. Carried out in 528 Chinese women, this study aimed to explore the relationships between skin characteristics, methods of application, and the potential for pilling. These still emerging data highlight the multifactorial nature of pilling.

Certain skin characteristics appear to be associated with a greater tendency to pill. The 2024 study showed that volunteers who experienced pilling when a sunscreen was applied alone on clean skin had reduced sebum levels, lower skin hydration, and a slightly higher skin pH.

However, these variations remain subtle and within “normal” physiological ranges, and do not reach the clinical thresholds characteristic of dry skin. They therefore represent relative tendencies, where having these skin characteristics can influence the surface properties of the skin and thus make it more prone to pilling, without any specific skin profile being definitively implicated.

Skin that contains less sebum has reduced natural lubrication, which can limit the spreadability of cosmetic formulations during application and thereby increase friction forces. In addition, a higher skin pH can modify the electrical charge of skin proteins as well as that of the polymers present in formulations. Yet the polymers used in cosmetics — such as carbomers or acrylates — are sensitive to pH. It influences their conformation, their degree of swelling, and their ability to adhere to the skin surface. These changes can in turn alter the formation of a uniform film.

Pilling can also occur when the skin has not been properly cleansed or exfoliated. Dead cells, cosmetic product residues, pollution particles, and all other impurities that build up on the skin’s surface create an uneven layer that can interfere with the adherence and absorption of skincare products. These elements act as mechanical anchoring points, where they promote the aggregation of formula components and contribute to the formation of clumps—a mechanism similar to the “pilling” observed in textiles.

Certain ingredients are particularly likely to cause pilling at higher concentrations when they come into contact with other formulations, such as high–molecular weight hyaluronic acid, polyglutamic acid, film-forming polymers (acrylates, carbomers), gums (thickening agents), pigments (iron oxides), and mineral UV filters (titanium dioxide, zinc oxide). These ingredients tend to create a film on the skin’s surface. When combined, these films can become unstable and break apart under mechanical stress.

The 2024 study showed that 80% of the observed pilling cases occurred when sunscreen was applied on top of a base product. Mineral filters, such as zinc oxide or titanium dioxide found in sunscreen, form particulate films that can be less flexible and more sensitive to friction. However, this does not mean that mineral sunscreens should be avoided.

If you apply a moisturizing cream before a facial serum, the serum can remain on the surface of the skin. In fact, when they are applied in the wrong order, the cream will limit or even prevent the serum from penetrating into the skin. Thicker formulas that are rich in polymers form an occlusive barrier on the skin’s surface. The active molecules in a lighter, water-based serum can no longer pass through this layer and therefore remain suspended on the surface, forming small granules that can be felt under the fingers when subsequent layers are applied.

Using excessively large amounts can lead to a buildup of material on the skin’s surface. This excess forms an unstable film that may break apart when the next product is applied or under repeated friction. This phenomenon is even more pronounced with formulas that are highly concentrated in thickening agents.

The way skincare products are applied also plays a decisive role in the appearance of pilling, independently of the formulas used. The 2024 study showed that rubbing motions—whether circular or linear—are the application methods associated with the highest number of pilling events. Mechanical friction generates shear forces that weaken the films formed on the surface of the skin, promoting the aggregation of polymers into small visible particles.

• LIU S. & al. Understanding the causes of skincare product pilling. Skin Research and Technology (2024).