COCOAMIDE DEA? It is suppose to be a lather booster. In addition to glycerine and LSLA...has anyone used this?
I have. Cocamide DEA is short for coconut fatty acid diethanolamide. It's one of a class of surfactants called fatty alkanolamides that are used as foam stabilizers and, in liquid compositions, thickeners or jelling agents. It comes in fairly concentrated form, which is its attraction in tablet formulas, that is, it's not bringing in much water, although in liquid products fatty diethanolamides have been relatively in disfavor for years for a combination of good & bad reasons.
One bad reason is that someone doing some routine screening tests found an increase in tumors in rodents injected with a certain fatty DEA. This is what you call a fluke. No good reason to think it would be backed up if investigated further.
A mostly bad reason is that monoethanolamine, and to a lesser extent diethanolamine, which will be present in small proportion as a byproduct in these amides, can undergo reactions with nitrites (and indirectly with nitrates) in the digestive tract to form significantly carcinogenic nitrosamines. I have no reason to think these pose a particular danger greater than the ethanolamines that are present in our bodies as necessary metabolic intermediates and are even popular these days in dietary supplements. However, the industry has been scared off enough from the DEAs to switch to an isomer class, MIPAs, as foam stabilizers. Fool's errand IMO.
The good reason for using something other than a fatty DEA is that they are irritating to eyes and skin compared to other nonionic foam stabilizers, and to other foam stabilizers in general. The chief nonionic foam stabilizers that fatty alkanolamides were long in competition with are amine oxides, as used for example in Joy and other hand dishwashing detergents. These actually reduce the irritancy of many anionic surfactants they're mixed with. However, since they're normally supplied at 30% solution in water, you may not find them convenient to use to make a solid product.
If you do use cocamide DEA (or lauramide DEA or lauric MIPA or others of that nature), you should use only a small amount compared to your chief foaming surfactant -- although some formulators have used a lot successfully. It's just my recommendation for mildness's sake that if you're using, say, SLSA, that it be present in an actives ratio of about 8:1 to fatty alkanolamide.
If you can work with betaines, I think you've got something even better there than nonionic foam stabilizers, but even more so tricky to formulate in solids.
However, even if you work with the most irritating of these choices, the fatty alkanolamide (such as cocamide DEA), even though it is by many measures more irritating than SLSA, by using it you can still make a product that in practice will be less irritating than using SLSA as the only surfactant. This apparent paradox is resolved by seeing that the foam stabilizer makes the bubbles last so much longer that you can use much less total surfactant per bath. The bath water will be sudsier, yet less irritating and less grease cutting. A lot of these recipes that rely on one surfactant alone, such as the SLSA here, count on making the bath water very soapy. Since the object is not to get you clean with something like this in the bath water -- a quick swipe with actual soap would work better -- but just to produce foam for your amusement (and prevent bathtub ring when you do use soap), maximizing the ratio of foam to detergency is a good thing.
