Nan Feyler, chief of staff for the Philadelphia Department of Public Health, wrote this for "The Public's Health" blog.

Here's a quick quiz: What do Pink Bubble Gum, Peanut Butter Cup, Strawberry Shortcake, Gummi Bear, Mountain Dew Burst and Banana Split Dreams have in common? Are they (A) an assortment of candy, gum, and soda given out at children's birthday parties; (B) names of soaps, shampoos, and body creams used by preteens; or (C) flavors of liquid nicotine used in the reusable types of e-cigarettes?

If you guessed (C) you are correct. Those are flavors of liquid nicotine, sometimes called e-liquid or e-juice, which is heated to create a vapor. An e-cigarette user (a "vaper") inhales a blend of water vapor and nicotine mixed with flavorings and other chemical additives. Liquid nicotine is sold legally in stores and online in hundreds of flavors and a range of nicotine concentrations, including very high potency.

Liquid nicotine hazards

Heated discussion of e-cigarettes - and there will be plenty of it, given the U.S. Food and Drug Administration's first proposed regulations, released on Thursday - naturally focuses on the effects of inhaling the vapor. But liquid nicotine can be harmful to the nervous system when accidentally ingested or absorbed through the skin. It can cause other harmful effects, including rapid heartbeat, elevated blood pressure, vomiting, abdominal cramping, dizziness, and confusion. This concentrated liquid is significantly toxic even in very small doses, particularly for children. At higher doses it can cause seizures and death.

Last month, the American Association of Poison Control Centers issued a warning about electronic cigarette devices and liquid nicotine because of a 300 percent rise - just from 2012 to 2013 - in calls to poison centers about accidental poisonings by liquid nicotine. Just over half of the calls involved children under age six. Some required hospital emergency-room visits - not surprising when you consider that the nicotine comes in sweet, candylike scents and flavors.

Records of the poison control center at Children's Hospital of Philadelphia, which contributed to the tally, show 19 calls involving liquid refills, 13 of them for children under six. The most common symptoms were nausea and vomiting, but one was severe toxicity. Three were cases of product confusion: administering e-juice instead of eye or ear drops.

Makers are skeptical

E-cigarette companies, many of which are owned by the big tobacco manufacturers, have scoffed at the recent reports of increased poison-center calls. Jason Healy, president of Blu eCigs, owned by Lorillard Inc., the third-largest tobacco company in the United States, called the report part of "an ongoing attack on the e-cigs industry." Healy said "the product is for adult smokers, and therefore the responsibility for children's safety falls on the parents, just like bleaches and prescription medications. The focus should be on parenting and education, and not regulation."

Neither e-cigarettes nor e-nicotine are now regulated. Some cities, including Philadelphia, have passed local laws - led by New Jersey, which took statewide action in 2010 - to prohibit selling e-cigarettes to children and using them in locations where ordinary cigarettes are banned. The FDA rules proposed Thursday would bar sales to minors and require labels warning that nicotine is an addictive chemical.