Obviously not, otherwise it would not have an expiration date.
No I dont recommend eating anything after the Expiration date
Is it safe to eat coconut cream after expiration date
It is not recommended to take Mucines DM after its expiration date. Most medicines have a long shelf life, but they become ineffective after the expiration date.
No
Is it safe to take lipozene after it has
are fleet enemas safe to use after the expiration date
No.
salad dressing
no
Possibly, but it is not worth the risk. Cheese tends to develop mold after it reaches the expiration date, and the mold is not always easily visible. The manufacturers put the expiration dates on foods for the safety of consumers, so please, don't ever eat any food past the expiration date - it simply is not worth the risk. Food borne illnesses kill many people in the US every year.
The expiration date on most drugs tell you when the manufacturer is guaranteeing it will have the maximum potency. Taking a drug after the expiration date is taking a chance that it won't be as effective as a drug taken within the "guaranteed effective." So, in answer to your question, on the diphenhydramine, no one knows if it is safe. All you can say for sure, is the manufacturer will not guarantee the drug is 100% effective after the expiration date.