Recently there has been a new focus on the safety of spray tans - specifically regarding the active ingredient dihydroxyacetone or (DHA). DHA was approved by the FDA in 1977 when it was popularly used in tanning lotions. Unfortunately, these first generation products didn't work very well and resulted in turning the skin orange. Since then the formulas have been reworked and the results produce much better tans.
The FDA approved the use of DHA to be externally applied - they didn't envision it being used as a spray and as such, there are restrictions on its use.
Read more: FDA Regulation Means an Even Playing Field
The potential problem being discussed now is two fold: 1) inhaled or ingestion of the fumes (by both the consumer and the technician) as well as 2) potential absorption into the skin. We would expect that there will be more studies conducted to further understand these potential risks.
Read more: The 3 Worst Reasons Not To Wear Sunscreen
The take away is if you are going to use a spray tan you should follow the recommended procedures as outlined by the FDA: protect eyes, ears, nose and mouth - and DO NOT INHALE the fumes. As a side note, you should not be inhaling fumes generally, this goes for spray-on suntan lotion as well - yes it is more convenient - but if you shouldn't eat it - you shouldn't breath it..... Here is the link for the FDA: FDA Guidelines and Warnings forSunless Tanning Sprays and Lotions
Here is the article that has restarted this discussion on the safety of spray tans: Are 'Spray-On' Tans Safe? Experts Raise Questions as Industry Puts Out Warnings