Which of the following is an example of a rubefacient?

A rubefacient is a substance that causes redness of the skin by increasing blood flow to the area, typically through the dilation of blood vessels. Such products are often utilized for their soothing properties in the treatment of muscle soreness or joint pain.

Biofreeze is specifically designed to create a cooling sensation followed by increased blood flow, which can relieve muscle tension and discomfort. It contains menthol as its active ingredient, which acts as a rubefacient by stimulating the skin's sensory nerves. This stimulation results in a sensation that distracts the brain from the underlying pain, thus it serves both as a cooling agent and a rubefacient.

The other options serve different purposes. Vaseline is an occlusive agent that locks in moisture but does not have rubefacient properties. Coconut oil is primarily used for its moisturizing benefits and does not promote increased blood flow to the skin. Witch hazel is often used for its astringent properties and is not classified as a rubefacient. Thus, Biofreeze stands out as the valid example of a rubefacient among the provided choices.