Dimethicone vs PDMS: Are they the same?

What is the difference between the names?

There is no reason to pick one name over the other, even if the longer one looks better equipped for a chemistry exam. Silicone is the broader family, not a synonym for every form of PDMS. That family includes fluids, gels and rubberlike materials. A technical discussion of a silicone material is therefore not automatically describing a moisturizer you can put on your face.2

What does dimethicone do in skincare?

Dimethicone forms a thin, nongreasy layer on the skin and acts as an emollient, meaning it softens and smooths the surface. It also serves as a barrier ingredient. Dimethicone is insoluble in water but allows water vapor through; the film is not a waterproof seal. Its smoothing effect comes from filling gaps in the outermost skin layer, rather than changing the underlying skin structure.1

Silicone based facial moisturizers can suit oily skin because they provide moisturizing benefits without a greasy shine. For very dry skin, petroleum based barrier products are more effective at reducing water loss than silicone based barrier creams. A less greasy finish can be a perfectly sensible preference, without turning your moisturizer into a chemistry referendum. Choose between finished textures and functions, not dimethicone versus PDMS.13

How should you use a product containing dimethicone?

These are general moisturizer and barrier cream directions, not a special PDMS routine.

1. 1Apply a leave on moisturizer immediately after bathing, when it helps retain water already in the skin.
2. 2Adjust application to dryness. Slightly dry skin can need only a light moisturizer at night; drier skin needs more frequent application.
3. 3For a barrier cream, apply sparingly and reapply as necessary. Barrier products can persist for several hours, even after gentle washing.

Expect surface smoothing and moisture support, not a separate result from each name. Moisturizers have their greatest therapeutic effects within the first six hours after application, and regular use two to three times daily can be needed to maximize benefits. The application schedule belongs to the product and your skin's dryness, not to the abbreviation.4

Can the finished product still irritate skin?

Yes. Barrier creams are usually well tolerated, but preservatives, fragrances and other components can cause allergic contact dermatitis, an allergic skin rash. Some occlusive barrier creams can aggravate acne on the face, and most should not be applied directly to broken skin. Stop using a moisturizer if a contact dermatitis rash develops. Suspected ingredient allergy can be investigated with medical patch testing.34