Hey everyone. I have really bad anxiety, and this might seem random and odd, but it is a serious question. My Dad lent me his head and shoulders shampoo tonight. I noticed the bottle looked out of date, like it was from the 90's. I asked my Dad about it, and he said it was fine, he has been using it. I ended up looking at the expiration date, and it was literally from 1998 (funny I know haha). Anyways, I decided to still use it since my Dad said he had been using it and he has been fine. Now I am worried though, because that is 15 years old! I figure shampoo doesn't go bad as far as harming you, and if anything that it is just way less effective now and more runny. I was just curious if using that shampoo could have been damaging to my scalp, brain, etc?? Thank you!!!