What is the effect of using a smoothing serum on curly hair?

Using a smoothing serum on curly hair primarily serves to reduce frizz. Curly hair can often become frizzy due to its structure, which makes it prone to dryness and porousness, causing the cuticle to lift and create that frizzy look. Smoothing serums are formulated with ingredients that help to coat the hair shaft, seal in moisture, and make the cuticle lie flat. This creates a smoother surface, helping to manage and control frizz while offering a sleek appearance to the curls.

While the other choices may highlight potential benefits associated with various hair products, they don't specifically capture the primary function of smoothing serums on curly hair. For instance, enhancing curl definition is more associated with styling products like curl creams or gels, heat protection is a key attribute of some serums but is not the primary purpose for curly hair, and adding volume is generally more linked to volumizing products than smoothing serums. Thus, the most accurate effect of using a smoothing serum on curly hair is its ability to effectively reduce frizz.