(CNN) As anxiety surrounding the novel coronavirus swirls in the US, some stores are struggling to keep up with the demand for hand sanitizer. With the shelves empty and online pharmacies out of stock, people have resorted to making their own.

But think twice about joining them -- experts are wary and even caution against the idea.

Recipes for DIY hand sanitizer are popping all over the internet. A quick search reveals news articles, YouTube how-to's and step-by-step visual guides.

The World Health Organization even has an official guide to making hand sanitizer. But it's intended for populations that do not have clean water or other medical-grade products in place.

If made correctly, DIY solution could be helpful and even effective. But if made incorrectly, it can be downright harmful.

"I worry about people making their own sanitizer as it will be difficult to make sure that the concentrations are correct," Daniel Parker, assistant professor of public health at the University of California, Irvine, told CNN of the trend.

For hand sanitizer to be effective, it must have at least 60% alcohol content, according to the US Centers for Disease Control and Prevention.

Store-bought hand sanitizers will also often have emollients to counter the harshness of the alcohol on the skin. If you don't have that in your homemade recipe, you could risk hurting your hands, Sally Bloomfield, a professor at the London School of Hygiene and Tropical Medicine told the Guardian.

Like store-bought sanitizer, homemade sanitizer would be something you'd want to keep out of the reach of young children, too.

A 2015 analysis by the Georgia Poison Center found poison control center hotlines across the US had seen a nearly 400% increase in calls related to children younger than 12 ingesting the product. Ingesting even small amounts -- as little as two or three squirts in some cases -- can cause alcohol poisoning.

Just wash your hands

The best way to prevent transmission of the novel coronavirus is still with good old water and soap.

Parker advises that people wash their hands thoroughly for at least 20 seconds, avoid touching their face, cover their mouth when sneezing or coughing, and regularly clean surfaces.

But if you're in a bind and have to use hand sanitizer, there's a correct way to do that as well.

Whether it's a spray-type hand sanitizer or gel, make sure both of your hands are covered -- including between the fingers and under the nails -- and rubbed until dry. Also, if your hands are visibly dirty or greasy, hand sanitizer may not be as effective, according to the CDC.