Viscosity

Viscosity — a measure of a fluid's resistance to flow, essentially how thick or runny a formula feels. In skincare it determines whether a product pours like water, spreads like a lotion, or holds its shape like a balm, and it influences texture, application, and how a product is packaged.

Key points

• Higher viscosity means a thicker, slower-flowing product, while lower viscosity means a thinner, more fluid one.
• Viscosity is often adjusted with thickeners, gums, or gelling agents rather than by changing active ingredients.
• Temperature affects viscosity, so many formulas become thinner when warmed and thicker when cool.
• Viscosity influences user experience, spreadability, and the type of packaging a product needs, such as a pump versus a jar.
• It does not by itself indicate how effective or moisturizing a product is.

Frequently asked

Does a thicker product mean it is more moisturizing?

Not necessarily; viscosity describes texture and flow, while moisturizing ability depends on the specific ingredients, so a thin serum can hydrate as well as a thick cream.

Why does my product seem thinner in summer?

Viscosity typically decreases as temperature rises, so warmth from the environment or your hands can make a formula flow more easily.

Related topics

• What Is a Humectant?
• What Is the Skin Barrier?

This is a foundational entry in the SYNC Skin Encyclopedia and is expanded over time. Educational information only — not medical advice.