"The mechanism of action is unknown. Cilantro alone often does not remove mercury from the body; it often only displaces the metals form intracellularly or from deeper body stores to more superficial structures, from where it can be easier removed with the previously described agents. The use of cilantro with DMSA or DMPS has produced an increase in motor nerve function.98"

http://www.mercola.com/article/mercury/mercury_elimination.htm

In the same article.

"Adequate sulfur stores are necessary to facilitate mercury's binding to sulfhydryl groups.

Many individual's sulfur stores are greatly depleted which impairs sulfur containing chelating or complexing agents, such as DMPS or DMSA, effectiveness as they are metabolized and utilized as a source of sulfur. Sulfur containing natural substances, like garlic99 100 and MSM (methylsulfonylmethane) may also serve as an effective agent to supply organic sulfur for detoxification.101 Fresh garlic is preferred as it has many other recently documented benefits.102 103 104 The garlic is consumed just below the threshold of social unacceptability, which is typically 1-2 cloves per day."