There really are aphrodisiacs (Viagra, etc, are the real ones, and usually require a prescription, but there are over the counter ones usually based on folk remedies that may or may not actually work). Usually they are gender-specific, because women need different hormones to get them horny than men do. Which means there is a decent chance that she's not lying when she says it wasn't affecting her, since the one he got was quite clearly labeled for men.