What it is
Microcrystalline wax is a high-molecular-weight wax composed of fine, branched-chain hydrocarbons, distinguished from paraffin by its smaller crystal structure, higher flexibility, and greater ability to bind oils. In sunscreens it is most common in stick formats, where it provides the rigidity and shape retention that let the product be molded and applied directly. It also helps thicken oil phases, reduce syneresis, and impart a smooth, pliable feel.
Safety & warnings
Microcrystalline wax is generally well tolerated and non-sensitizing. Like other heavy hydrocarbon waxes it is occlusive and can contribute to a heavier, occlusive feel, which some users with acne-prone skin may find less comfortable, though it is not a recognized active sensitizer.
Origin & sourcing
Synthetic in the sense of being industrially refined; it is obtained from the heavier fractions of petroleum during dewaxing of lubricating oils, then purified to a cosmetic grade.
Questions everyone asks
How does microcrystalline wax differ from paraffin wax?
It has smaller, more irregular crystals, which makes it more flexible, more adhesive, and better at binding oil than the larger-crystal paraffin wax.
Why is it used in sunscreen sticks?
It gives the stick its solid structure and shape retention while keeping the product smooth and easy to glide on.