I noticed an old bottle of milk of magnesia in my refrigerator and saw that it had an expiration date printed: January 2015. Checking the ingredients, I saw only three: magnesium hydroxide, purified water, sodium hypochlorite. I understand that milk of magnesia is more or less a mineral solution. How could this require an expiration date? What would be the consequences of taking milk of magnesia past the expiration date?
(I see that this page discusses expiry dates on chemicals in the abstract; I don't know which of these arguments apply to milk of magnesia in particular, or any other over-the-counter dietary supplement or drug. As an IT professional, I have absolutely no experience or expertise in the physical or life sciences.)