Ever since the first cases of swine flu broke out earlier this year, demand for hand sanitizer has skyrocketed. Some makers of the gels are now scrambling to keep up with the demand.

The marketing research firm Panjiva recently estimated that 3 million kilograms of hand sanitizer were shipped in the 3rd quarter, compared to 1 million kilograms during the same quarter last year. Panjiva CEO Josh Green says that concerns over the H1N1 virus is the "most likely explanation" for the surge. Given the outlook for a particularly bad flu season, demand is only expected to rise further.

In response, companies like Purell are ramping up production and are urging customers not to hoard the product. Purell manufacturer Johnson & Johnson (JNJ) says that demand for Purell has been "heavy" since the first swine flu cases were reported.

J&J spokesman Marc Boston said in a statement:

"Due to the influenza A (H1N1) virus outbreak this past spring and resurgence this fall, Johnson & Johnson Consumer Companies Inc. has experienced heavy demand on supplies of Purell.

Boston said that the company is working to increase production for the remainder of 2009 and the beginning of 2010, but acknowledges that supplies could be limited in some areas:

"Because of this increase in demand, consumers may currently find limited supplies of Purell Instant Hand Sanitizer at certain retailers."

To date, nearly 400,000 people around the world have contracted lab-confirmed cases of swine flu. 4,700 have died from the illness since it was first identified in Mexico and the U.S. in April. Many countries have stopped counting individual cases of milder illness, which means the total count could be significantly higher.