A pox party, or flu party or flu fling, is a social activity where children are deliberately exposed to a virus to promote immunity. Such parties are typically organized by parents on the premise of building the immune systems of their children against diseases such as chickenpox and measles (which can be more dangerous to adults than to children) or flu. Such practices are highly controversial and are discouraged by public health officials. In the USA, if the exposure involves the United States Postal Service to swap contaminated items, the practice is illegal.
Effectiveness and risk 
Parents who expose their children to the virus in this manner believe that this method is safer and more effective than receiving a vaccination. Similar ideas have been applied to other diseases such as measles. However, pediatricians have warned against holding pox parties, citing dangers arising from possible complications associated with chicken pox, such as encephalitis, chickenpox-associated pneumonia, and invasive group A strep. Although such complications are not common, they can cause brain damage or death. Before the chickenpox vaccine became available there were 100 to 150 deaths from chickenpox among children in the U.S. annually. All of the illnesses the parties are intended to ameliorate, including not only chicken pox, but other diseases such as mumps and hepatitis A, can be life-threatening to children if treated inappropriately. The chickenpox vaccine is recommended by health officials as a safe alternative.
Some parents have attempted to collect infected material, such as saliva, licked lollipops, or other infected items from people who claim to have children infected with chickenpox. The parents use social networking services to make contact with these strangers. The unknown person then mails the potentially infectious matter to the requester, who gives it or feeds it to his or her child in the hope that the child will become ill. 
Experts say it is unlikely that these methods will transmit the chickenpox virus effectively or reliably, because the varicella virus cannot survive for very long on the surface of such items. However, it may be a reliable method of transmitting other diseases, including hepatitis B, group A streptococcal infection, and staphylococcal infections—potentially deadly diseases that the parents never intended to expose their children to. Additionally, deliberately sending infectious matter through the U.S. Postal Service is illegal.
Historically, smallpox parties and other forms of controlled inoculation reduced significantly the death rate due to smallpox (see Variolation). With the introduction of a smallpox vaccine, inoculations of wild smallpox virus fell into disuse.
Similarly, the rubella party was sometimes considered a rite of passage for pubescent females after the link between rubella infections early in pregnancy and severe birth defects was established, but before the development of effective rubella immunizations.
Flu parties 
During the 2009 flu pandemic in Canada, doctors noted an increase in what were termed flu parties or flu flings. These gatherings, as with the pox parties, were designed explicitly to allow a parent's children to contract the "swine flu" influenza virus. Researchers such as Dr. Michael Gardam note that because the pandemic is caused by a flu subtype that most people have had no exposure to, the parents are just as likely to get the disease and further the spread. Although these events were heavily discussed in the media, very few were confirmed to have happened.
See also 
- McNeil Jr, Donald G. (May 6, 2009). "Debating the Wisdom of ‘Swine Flu Parties’". New York Times. Retrieved 2009-05-07. "Chickenpox parties, at which children gather so they can all be infected by a child who has the pox, are often held by parents who distrust chickenpox vaccine or want their children to have the stronger immunity that surviving a full-blown infection affords and are willing to take the risk that their child will not get serious complications."
- Ghianni, Tim (November 12, 2011). "Swapping chicken pox-infected lollipops illegal". Reuters. Retrieved 2011-12-29. "A federal prosecutor is warning parents against trading chicken pox-laced lollipops by mail in what authorities describe as misguided attempts to expose their children to the virus to build immunity later in life."
- "Inside New York Chicken Pox Parties". Retrieved 10-09-2011.
- Henry, Shannon (September 20, 2005). "A Pox on My Child: Cool!". The Washington Post. pp. HE01
- Brown, Eryn (November 4, 2011). "'Pox parties': Coming to a mailbox near you?". The Los Angeles Times.
- rubin, rita (Nov 2011). + publisher=MSNBC: Today "Chickenpox lollipops? Some moms may be sending in mail".
- DeNoon, Daniel J. (September 29, 2005). "'Pox Parties' Pooh-Poohed".
- News staff, CTV (3 July 2009). "Doctors say 'flu parties' not a good idea". CTV News. Retrieved 3 July 2009.
- "The Golden Boy and the Invisible Army"
- The return of the measles party
- Playing chicken: Some parents want children to catch chicken pox
- Mothering Magazine article