I was curious about what it’s in, so I looked up Wikipedia:

Diethanolamine is widely used in the preparation of diethanolamides and diethanolamine salts of long-chain fatty acids that are formulated into soaps and surfactants used in liquid laundry and dishwashing detergents, cosmetics, shampoos and hair conditioners.[5] In oil refineries, a DEA in water solution is commonly used to remove hydrogen sulfide from sour gas. It has an advantage over a similar amine, ethanolamine, in that a higher concentration may be used for the same corrosion potential. This allows refiners to scrub hydrogen sulfide at a lower circulating amine rate with less overall energy usage.

In things found at home it appears to be mainly soaps and cosmetics. These substances in particular:

Some of the most commonly used diethanolamides include:

   - Cocamide DEA
   - DEA-Cetyl Phosphate
   - DEA Oleth-3 Phosphate
   - Lauramide DEA
   - Myristamide DEA
   - Oleamide DEA