The way a sunscreen feels, layers and sits on the skin can have a big impact on the overall product experience.
For some users, sunscreen may occasionally ball up or flake when applied with other skincare or makeup. This is commonly known as pilling. Formula stability is a separate consideration and relates to whether the product maintains its intended appearance, texture and consistency over time.
For brands developing SPF, understanding these behaviours can help inform formulation development, product testing and the intended user experience.
Why Does Sunscreen Pill?
Pilling happens when product gathers into small flakes or rolls on the surface of the skin instead of sitting smoothly.
It may become noticeable while sunscreen is being applied or when another product, such as foundation, is layered on top.
There is not always one simple cause.
Pilling can be influenced by:
- The sunscreen formulation
- The skincare products used underneath it
- Makeup applied over the top
- How much rubbing occurs during application
- How quickly products are layered
- Individual skin characteristics
This is why the same sunscreen may layer differently depending on the person’s routine and the products being used with it.
How Product Layering Can Affect SPF
A typical morning skincare routine may involve several products before sunscreen is applied.
Serums, moisturisers, facial oils, primers and sunscreen can all leave different materials on the skin. Adding makeup introduces another layer again.
When several products are applied together, the way those formulas interact can influence the finished result.
For example, pilling may become more noticeable when:
- Several layers are applied in quick succession
- One product has not had time to settle before the next is applied
- Products are repeatedly rubbed over one another
- A particular combination of skincare, SPF and makeup does not layer smoothly
For brands developing a daily facial sunscreen, this is worth considering because SPF is rarely used on completely bare skin.
Understanding how the product fits into an everyday skincare routine can help shape the desired texture, finish and application experience during development.
Do Silicones Cause Sunscreen Pilling?
Silicones are often associated with pilling, but they are not automatically the cause.
Silicones are commonly used in skincare and sunscreen formulations to influence areas such as spreadability, texture and skin feel.
A formula containing silicones can still layer smoothly.
Pilling is better considered in the context of the complete formulation and the other products being used alongside it.
Film-forming ingredients, polymers and other materials can also influence the way products behave when layered.
For brands, focusing on the overall product experience is generally more useful than trying to avoid one ingredient purely because it has been associated with pilling.
Application Technique Can Make a Difference
How sunscreen is applied can also influence how it sits on the skin.
Repeated rubbing may disturb skincare layers underneath and make pilling more noticeable.
Allowing products to settle between layers and applying sunscreen evenly can help create a smoother finish.
If pilling occurs, consumers may find it helpful to:
- Allow skincare products time to settle before applying sunscreen
- Apply products in even layers
- Avoid excessive rubbing once the sunscreen has been spread
- Notice whether pilling only occurs with certain product combinations
- Follow the sunscreen’s application directions
Using less sunscreen than directed is not the ideal way to address pilling. Sunscreen should still be applied according to the product instructions.
The Skin Can Also Influence How Products Layer
The products being used are only one part of the application experience.
Individual skin characteristics may also influence how skincare and sunscreen behave once applied.
Factors such as skin hydration and oil levels can affect the way products spread and sit on the skin.
This helps explain why one person may notice pilling with a particular combination while another person does not.
For brands, considering different skin types and common skincare routines during product evaluation can provide useful feedback about the way a sunscreen feels and layers in everyday use.
What Does Formula Stability Mean?
Formula stability is different from pilling.
Pilling happens during application. Stability relates to how the formulation performs over time.
Many sunscreen products are emulsions, meaning different components of the formulation are brought together to create a uniform finished product.
The aim during formulation development is to create a product that maintains its intended appearance, texture and consistency as it progresses through the appropriate testing program.
Several factors can influence formula stability, including:
- The formulation itself
- Ingredient interactions
- Manufacturing process
- Storage conditions
- Product format
- Packaging considerations
These areas are considered during development rather than being assessed only once a product reaches commercial production.
How Is Formula Stability Assessed During Development?
A sunscreen can look and feel right when a lab sample is first produced, but the development team also needs information about how the formulation performs over time.
Stability testing provides that information.
The formulation is monitored under defined storage conditions and assessed against the requirements established for the product.
The exact testing program will depend on the formulation and stage of development.
Results can help the development and quality teams understand whether the product is ready to continue through development or whether further review is required.
This is part of the normal development process for many cosmetic and personal care products.
Pilling and Formula Stability Are Different Considerations
Although both can influence the way a consumer experiences a sunscreen, pilling and formula stability should not be treated as the same issue.
Pilling relates to how the product behaves during application and layering.
Formula stability relates to whether the formulation maintains its intended characteristics over time under defined testing conditions.
A sunscreen that pills when combined with a particular skincare product is not necessarily unstable.
Likewise, stability testing does not tell a brand everything about how a sunscreen will behave underneath moisturiser, primer or makeup.
Both areas can be considered during development, but they provide different information about the finished product.
Developing SPF With the User Experience in Mind
For brands, the first step is being clear about how the sunscreen is intended to fit into the consumer’s routine.
A daily facial SPF designed to sit comfortably underneath makeup may have different product goals from a sunscreen intended for sport, swimming or outdoor use.
A useful SPF brief might include preferences around:
- Texture
- Finish
- Spreadability
- Absorption
- White cast
- Makeup compatibility
- Overall skin feel
These details give the formulation team a clearer picture of the experience the brand wants to create.
During sample review, feedback should also be as specific as possible.
Instead of simply saying a sunscreen “doesn’t layer well”, it is more useful to explain what happened, when it happened and which other products were being used.
That information gives the formulation team more context when reviewing the sample.
How Brands Can Assess SPF Layering
Brands do not need to become formulation specialists to provide useful feedback.
Simple real-world observations can be helpful during development.
When reviewing a sunscreen sample, consider:
- How easily does it spread?
- How does it feel once applied?
- Does the finish change after a few minutes?
- How does it sit over common skincare products?
- How does makeup apply over the top?
- Does additional rubbing affect the finish?
- Does the experience match the original product brief?
The goal is not to test every possible skincare combination.
It is to understand how the product behaves in the types of routines it is being designed for.
SPF Development at Delta
Delta works with skincare and personal care brands across SPF formulation development and commercial manufacturing.
During development, brands can review lab samples and provide feedback on areas such as texture, finish, spreadability and the way the product sits on the skin.
Stability testing can also provide information about how the formulation performs over time under defined storage conditions.
Considering both the formulation and the intended user experience during development gives the team a clearer understanding of what the finished product is expected to achieve before moving towards commercial manufacturing.
FAQ: SPF Pilling and Formula Stability
Why does sunscreen ball up on the skin?
Sunscreen pilling can be influenced by the sunscreen itself, products layered underneath or over it, application technique and individual skin characteristics.
Can skincare underneath sunscreen cause pilling?
Yes. The way different products interact when layered can influence whether pilling occurs. Allowing skincare products time to settle before applying sunscreen may help.
Do silicones cause sunscreen to pill?
Not necessarily. Silicones are commonly used in skincare and SPF formulations and do not automatically cause pilling. The complete formulation and the products being layered together are more relevant.
Why does sunscreen pill under makeup?
Pilling under makeup can occur when the skincare, sunscreen and makeup layers do not sit smoothly together. Application technique and repeated rubbing may also contribute.
Is pilling the same as formula separation?
No. Pilling happens during application on the skin. Formula stability relates to how the product maintains its intended appearance, texture and consistency over time.
How can brands assess sunscreen layering during development?
Brands can review how the sunscreen spreads, settles, feels and behaves over common skincare products and underneath makeup. Specific feedback gives the formulation team useful information during sample refinement.
Developing an SPF Product?
Delta works with brands across SPF formulation development, stability testing, scale-up and commercial manufacturing.
Speak to Delta about your SPF product, desired user experience and manufacturing requirements.