Spray tanning solutions are available in many different concentrations of DHA (Di-Hydroxy-Acetone).
The concentration of DHA does not necessarily determine the quality of the product.
A lower concentration of DHA is typically for light touchups and fair skinned people, while heavier concentrations are for deeper tans and darker skin tones.
Of late, numerous 'new' formulas are arriving on the market touting miracle effects of their branded spray tanning solutions.
Choosing a quality product may be a mere preference to a particular company's ingredient.
While DHA is the only effective base chemical for sunless tanning, some manufacturers are experimenting with other chemicals to achieve a sunless tan.
No other product is currently FDA approved for sunless tanning, so if it does not contain DHA, as it's primary tanning ingredient you may be disappointed in the results.
There are also claims that an additional agent is added to enhance the tan, these products should be tested by you before purchasing in order to ascertain the manufacturer's claims.
You can always ask for a free sample or an inexpensive sample (about 3 ounces is sufficient to give you a test tan).
Be careful to not get wrapped up in sales hype, if the product you have been using is meeting or exceeding your expectations, a new product may not necessarily perform as well as your regular spray tanning solution.
As with anything you should be skeptical about 'miraculous' ingredients that are home-brewed by unscrupulous dealers.
If their product is nearly as fantastic as they claim, offering a free sample to get your continued business should be no problem for them, and acts as a goodwill gesture towards you as a customer.
Quality spray tanning solutions from reputable dealers are easy enough to find, and if you are unsure about a particular product, it is best to pass it up unless you have tested it for yourself or you receive a recommendation by a reputable company.