US parents who reportedly buy mail order lollies infected with chickenpox to try to help their children build up immunity from the virus are being warned the practice could be dangerous. The treats have apparently emerged following chickenpox "parties" - where parents get their youngsters together with an infected child so they catch it, in the belief it will strengthen their defences. Such gatherings have become popular in recent years following health concerns related to vaccinations. But Jerry Martin, US attorney for the Middle District of Tennessee, said he was concerned by reports in Phoenix and Nashville of people going on Facebook to find lollipops, saliva or other items from children who have chickenpox. He said: "Can you imagine getting a package in the mail from this complete stranger that you know from Facebook because you joined a group, and say, 'Here, drink this purported spit from some other kid?'" Mr Martin said it was a federal crime to send diseases or viruses across state lines in the post. Sending snacks laced with chickenpox would be illegal under the same law that makes it illegal to post infectious diseases such as anthrax. He said a conviction could lead to a jail sentence between a few months and 20 years. Some parents are worried about their children having vaccinations Mr Martin said the items were sought by parents who do not want to give their children vaccines. He said he could not confirm nor deny his office was investigating or seeking charges against anyone. Isaac Thomsen, a specialist in paediatric infectious diseases at Vanderbilt Children's Hospital, said it was unlikely children would pick up chickenpox from the items. "If there's a very high load on the virus and shipped very quickly, it's theoretically possible," he said. "But it's probably not an effective way to transmit it. It typically has to be inhaled." However, Mr Thomsen warned that the lollipops could carry more dangerous viruses, including hepatitis. According to reports, parents have turned to a Facebook group called "Find a Pox Party in Your Area" to link people looking to share the virus. One of the Facebook postings from Wendy Werkit, of Nashville, offered a "fresh batch of pox in Nashville. Shipping of suckers, spit and Q-tips available tomorrow $50 via PayPal". Ms Werkit told WSMV-TV in Nashville: "They can't get (chickenpox) the normal way anymore by just naturally catching it and naturally getting the immunity for life." Vanessa The Google Girl.