system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: if baby shampoo leaves babies tear-free, what makes adult shampoo so painful and why do we need it?
gpt
"Tear-Free Baby" or "Minimal Eye Irritation" shampoo's will have a lot of similar ingredients to adult products, however in much less of a concentration (less added), diluted. 
The acidity or PH of baby shampoo is closer to that of a normal human body, if you ever got lemon juice (high acidity) in your eye you know it burns. Water is generally neutral PH and is closer to that of the human body. 
Some baby shampoo's also contain eye anesthetizing agents that numb the pain that is caused by the shampoo. This allows for stronger ingredients that actually do the cleaning.
Basically adult shampoo will have harsher chemicals, given that as adults we should be at a reduced risk of getting it in our eyes. Not always true though. 

Hope that helps you.