Hillary Clinton has asked the maker of the the EpiPen to voluntarily lower the price of the lifesaving allergy treatment, which has jumped by over 400 percent in the past few years. Senators Susan Collins of Maine and Claire McCaskill of Missouri also requested pricing information from the manufacturer, Mylan NV, within two weeks.

Clinton called the price hit "outrageous" and "the latest troubling example of a company taking advantage of its consumers" in a statement. She’s not alone. Several senators have been pressing Mylan over the price hikes. The American Medical Association — the nation’s largest physician organization — made a similar plea, with AMA president Andrew Gurman calling the price hikes "exorbitant" in a statement. These rising prices have been a burden on consumers who, depending on insurance, sometimes pay full price or otherwise have very high co-pays for the widely used treatment.

People with severe allergies stab themselves with the EpiPen to deliver a hormone called epinephrine that ends an allergy attack. Nine years ago, one EpiPen cost about $57. Now, a two-pack costs more more than $600. The dramatic price hike is even more astonishing given that epinephrine itself is incredibly cheap: there’s less than $1 worth of the hormone in each EpiPen. The cost comes from the design of the pen, which is necessary to make sure someone can easily use it and get the right dosage.

Several factors have made it easier for Mylan to hike up the prices. First, epinephrine is an unstable hormone; EpiPens need to be replaced so that the dosage inside remains correct. Because doctors advise having one around at all times, many people buy many EpiPens just in case. And six years ago, the US Food and Drug Administration ruled that the devices have to be sold in packs of two because some children need more than one at a time to fight an allergy attack.

The EpiPen controversy follows a similar controversy last year, when Martin Shkreli, chief executive of Turing Pharmaceuticals, drastically raised the price of a key cancer and AIDS drug. A new paper from Harvard Medical School researchers analyzing the phenomena of high drug prices concluded that FDA regulations and federal law work together to protect drug companies from competition. For Mylan, the EpiPen is a key product that provides 40 percent of its operating profit.

Accordingly, Clinton used this opportunity to promote her plan to lower prescription drug costs by increasing competition among drug companies to drive prices down.

A spokesperson for Mylan did not immediately respond to a request for comment.