Your mother or father probably passed down this bit of wisdom: If it sounds too good to be true, it probably is, so don't be a sucker who gets seduced by false advertising. Every parent has their own version!
So what about all the zillions of different products on the market now, all supposedly "guaranteed" to grow you a bigger set of tah tahs? I've been in the breast business a long time and have yet to see one that works (short of surgical augmentation, which of course is neither pill nor potion). Every one of the miracle makers is a gyp.
The only pill per se that may add volume to your rack is a hormone tablet - as in an oral contraceptive (the Pill) or hormone replacement therapy. That additional estrogen can enhance your silhouette, but that's a pretty poor reason to put a powerful substance like estrogen into your body. Not only that, but the extra estrogen may even increase your risk of developing breast cancer and potentially losing one or both breasts.
Remember doing those "breast" exercises in high school - the hand squeezes and the flexing of your chest muscles that were supposed to enlarge your breasts? Well, while those exercises won't actually increase your breast size, they might increase the size of the pectoralis muscle located underneath your breasts. I'm not aware of scientific evidence for this but I imagine if you did them diligently every day, they might upgrade your chest size if not your cup size.
The more pressing question on my mind is this: How do these pills and potions get on the market in the first place, and who is allowing their makers to make such false claims? It turns out that since "breast-enhancing" products aren't regulated by the FDA, their manufacturers can say whatever they want and nothing bad will happen to them. And if a few simple folk order their product for $59.95, then those sillies might even convince themselves that somehow their breasts did grow! The mind is a powerful thing.


