Astringent

Ingredients with the astringent function help to temporarily reduce the feeling of greasiness and make the skin look more "collected". They cause a slight superficial tightening of the tissues, so after application, the skin may appear more matte, and the pores may be less visible visually. In cosmetics, such components are most often used in tonics, aftershave lotions, scalp products and formulas for oily and problematic skin. In the official European CosIng database, this function is described as creating a feeling of skin tightening and tissue compression. (accessdata.fda.gov)

In practice, such substances are useful where you need to quickly reduce shine, reduce the discomfort of excess sebum and refresh the skin. They can also be appropriate for hair and scalp: they help to make the roots look less greasy and add a sense of cleanliness after application. At the same time, we are not talking about "pore narrowing" in the anatomical sense, but rather about the temporary visual and sensory effect. If the skin is sensitive or damaged, pronounced tightening can be perceived as dryness, so the formula usually requires a balance with moisturizing and softening ingredients. (accessdata.fda.gov)

Typical examples of ingredients with this function are Hamamelis Virginiana (Witch Hazel) Water/Extract and zinc salts, such as Zinc Sulfate or Zinc Acetate. Witch hazel has long been used in products with an astringent and soothing profile, and zinc compounds are known as substances that can be used topically as an astringent. That is why they are often included in products for oily skin, spot treatments and refreshing lotions. (accessdata.fda.gov)