What are the harmful side effects of using a delay cream for sex?

Allergy: Repeated use of "caines" (anesthetic) creams to delay orgasm is usually not harmful but the "caine" drugs notoriously cause allergic reactions with repeated use! Hope this helps Dr Z

Delay Cream: besides possible irritation to either party, I don't know of any harmful effects to these creams. They are all local anesthetics meant to dull the sensation to the tip of the penis.