This is information that is currently circulating round, due to CND's (more known currently for Shellac gel varnish) Creative Director Jan Arnold being interviewed in their MORE magazine saying that it is not possible for them to create a neon varnish because of US Food and Drug administration (FDA).
However, after reading the FDA's website and product information page this might not be the case:
"The law says that color additives have to be approved by FDA for use in cosmetics, including color additives in face paints and other cosmetics that may be used around Halloween time. It also includes theatrical makeup.
Plus, FDA has to decide how they may be used, based on safety information. A color that's OK on your tough fingernails or your hair may not be OK on your skin. Colors that are OK for most of your skin may not be OK near your eyes."
UK wise we are deemed OK to use this and you can find them everywhere, notable Nails Inc. who are launching they're own range for Summer.
Source: FDA and Source: Occupational Safety and Health Administration (OSHA)
Currently in the UK this is all being investigated by HSE (Health and Safety Executive) after it was suggested in February that investigations should start taking place due to what was happening overseas. They're main concern is salon technicians who specialise in this field are constantly exposed to this gas (not doubting that this is the same for the US). They're next formal scheduled meeting will not be until 30th June; They are currently promoting glove use in hair salons to reduce skin exposure. (Source), for now the matter is precaution when using until further is heard.
Please note: At the moment shop brought kits are not affected, it is only products known as "Brazilian Blowouts" that are salon based. However with any hair care product (dyes, etc.) manufactures instructions must always be followed for your protection.