No-rinse acid sanitizer - is there a risk?

I think that one should rinse after Star San usage although the manufacturer claims the opposite.

To determine the ingredients of a commercial chemical mixture like Star San, one can look in the material safety data sheet. The active ingredients are phosphoric acid, dodecyl benzene sulfonic acid and a "proprietary" compound. Little amounts of phosphoric acid (as described in other answers) are safe even if they are in the beer. However, dodecyl benzene sulfonic acid is problematic: it's a surfactant and even little traces of these substances make beer foam unstable. Therefore, I don't use dishwashing liquid or Star San for cleaning or sanitizing brewing equipment. As replacement, I'm using iodine solution and rinse with tap water. Tap water should be nearly free of germs if the pipes and the faucet aerator are clean.

Star San contains this "proprietary" compound. Without a specification of this compound, I'm unable to determine if Star San is save to use for beer brewing without rinsing.

I think using disinfectants like Star San without rinsing for commercial brewing is illegal in some countries like Germany. In DIN 10516 standard it's written that removing of the cleaning or disinfection agents is mandatory except if the substances are harmless and permitted food analogs or additives. As far as I know, dodecyl benzene sulfonic acid and probably the "proprietary" compound are not permitted as food analogs or additives.

Star-San used in the correct concentration won't affect your beer. If you do decide to rinse, boil enough water to rinse and allow it to cool. Otherwise, you risk re-introducing contaminants.

Starsan actually breaks down and is consumed by the yeast in your beer as if it was nutrient so long as you use it as directed. So seriously don't fear the foam.

The difference between "drinking" tap water and "rinsing" with it is that our body can handle whatever small amount of bacteria may be in the water, but the conditions for fermenting beer are also ideal for bacteria to grow and multiply so that insignificant amount of bacteria we normally drink can grow under the right conditions (in the fermenter or bottle) and spoil a batch.

That being said, beer is more resilient than we give it credit for.

Perhaps I'm failing to "get with the program" on this no-rinse sanitizer thing, but I personally like rinsing. I like the fact that bleach-and-water does a great job sanitizing, and then I'm glad I've got clean tap water to rinse it all out.

I don't care that the foam isn't going to hurt my beer, I still don't want to be drinking even trace amounts of sanitizer.

I had similar fears after reading the warnings on the label until I read Palmer's How to Brew, 3rd Ed. p. 23, as part of his discussion of different methods of cleaning and sanitizing:

StarSan is only effective when the pH of the solution is less than 3.5. ... This is also the reason it is a no-rinse sanitizer: When the fermenter or bottle has been drained and filled with wort or beer, the higher pH of the wort and beer neutralizes the sanitizing capability, so that the yeast are unaffected. ... [E]ven though there can be a huge amount of foam in vessels like carboys after draining, it will have no effect on fermentation or flavor.

He even says that StarSan and Final Step (both acidic sanitizers) are his "preferred sanitizers" for whatever he can't easily do in the dishwasher.

Regarding the scary warnings on the label, he adds:

Because it is listed as a sanitizer and bactericide by the FDA and EPA, the container must list disposal warning that are suitable for pesticides. Do not be alarmed; it is less hazardous to your skin than bleach.

The amount of acid in a properly mixed batch of StarSan is less than in a bottle of Coke. I've been using it for years and find it extremely effective as a sanitizer. I never rinse and it has had no adverse effect on my beer. In fact, I've won several awards since I started using it. The commonly heard refrain is "Don't fear the foam!"