The Click'n'Vote - 'What is the most challenging factor when developing high SPF formulations?' - question was in itself a bit more challenging than some of the questions posed to the SpecialChem Community in the past. The reason for this is that it is sometimes difficult to achieve a high SPF without taking all these factors into consideration, especially with the latest FDA sunscreen regulations that just went into effect this past June. But this is how the Community responded to this challenging question - and it was a fairly large response. My comments are based on the most popular response down to the least popular response even though in this case all the responses should be considered when formulating any OTC product.