Why do some skincare products pill?

Similar to flaking skin, pilling is characterised by the formation of small aggregates on the skin surface during the application of skincare products. For a long time, this phenomenon was based mainly on empirical observations until the publication in 2024 of the first clinical study devoted to it, conducted by LIU S. et al. in the journal Skin Research and Technology. Conducted in 528 Chinese women, this study aimed to investigate the relationships between skin characteristics, methods of application and the propensity to pill. 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 to 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, in which having these skin characteristics may influence the surface properties of the skin and thus make it more prone to pilling, without any particular skin profile being definitively implicated.

Skin that is lower in sebum has reduced natural lubrication, which can limit the spread of cosmetic formulations during application and thereby increase frictional forces. Furthermore, a higher skin pH can modify the charge of skin proteins as well as that of polymers present in formulations. Yet the polymers used in cosmetics — such as carbomers or acrylates — are pH-sensitive. The pH influences their conformation, their degree of swelling, and their ability to adhere to the skin surface. These modifications can in turn impair the formation of a homogeneous film.

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

Certain ingredients are particularly prone to causing 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 surface of the skin. When combined, these films can become unstable and fragment under mechanical stress.

The 2024 study showed that 80% of observed pilling cases occurred when applying sunscreen over a base product. Mineral filters, such as zinc oxide or titanium dioxide present in sunscreen, form particulate films which may be less flexible and more sensitive to friction. However, this does not mean that mineral sunscreens should necessarily be avoided.

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

Using quantities that are too large can lead to a build-up of material on the skin surface. This excess forms an unstable film, which may fragment when the next product is applied or as a result of repeated friction. This phenomenon is even more pronounced with formulations that are highly concentrated in thickening agents.

The way in which 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).