eli5: What is it in “adult” shampoos that makes our eyes hurt and how exactly are kids shampoos formulated to be “eyefriendly”?

Question

eli5: What is it in “adult” shampoos that makes our eyes hurt and how exactly are kids shampoos formulated to be “eyefriendly”?

In: Chemistry

Answer 1

There was an (apparently incorrect) rumor when I first heard this answered that baby shampoo merely deadened your eye nerves so you just couldn’t feel the ouch though the ouch (damage) was still there. Now, the latest answer I’ve read is that the surfactants in baby shampoo are different than in regular shampoo. Surfactants remove oils because the molecules have one end that likes water and one end that likes oil allowing the oil to be washed away with the shampoo. The surfactants in baby shampoo are longer than in regular shampoos. This makes them less effective, but not as harsh, but since babies aren’t oil factories it works fine.. Sodium lauryl sulfate (C12H25NaO4S) [or (CH3(CH2)11SO4Na)] or sodium laureth sulfate (C14H29NaO5S
or (CH2)11(OCH2CH2)nOSO3Na) are common in regular shampoo, my bottle of baby shampoo has sodium trideceth sulfate which is oddly even harder to find only one formula for but appears to be (C19H39NaO7S). That 39 in the middle kind of shows how long the molecule is.

Edit: redditors who remember more of their Chemistry than I do of my decades old HS classes say the C19 shows the length rather than the H39. Which makes sense as H only attaches on one end and won’t form a chain.