Which treatment should be applied in the same direction as hair growth?

The correct answer is soft wax. When applying soft wax for hair removal, it is essential to apply the wax in the same direction as the hair growth to ensure effective adherence of the wax to the hair. This technique helps to secure the hair strands, which allows for a smoother and more efficient removal process. By following the natural growth pattern, the wax can properly capture the hair, resulting in less breakage and discomfort.

In contrast, clay masks, vitamin C serums, and warm towels do not involve the same technique of application relative to hair growth. Clay masks and serums are typically applied evenly across the skin for even coverage and absorption, while warm towels are used for relaxation or to precondition the skin before other treatments but do not have a specific directional application related to hair growth. Therefore, soft wax is the only treatment in this context where the direction of application relative to hair growth is crucial for effectiveness.