Soap is another good example, if you include corrosive materials. And while you're not ingesting it, you're likely absorbing some amount via your skin on a regular basis.
One of the necessary components of soapmaking is lye, or sodium hydroxide, which is so alkaline that it will eat through flesh. It also has an exothermic reaction with water, to the point that it can be explosive if you pour the water onto lye instead of the lye into the water (the former mixes it too fast, while the latter allows for a slower mix and more time for things to settle a little bit).
However, due to the chemical reaction that lye undergoes with fatty acids, you're left with an inert and safe compound.
Additionally, sodium hydroxide is often used on pretzels before baking, but the (much more subtle) reaction with the dough renders it nonhazardous, as the end result is a change in the pH of the surface of the dough, which gives you that nice brown, chewy exterior. (Sodium bicarbonate or sodium carbonate can be used for this purpose, as well.)
Borax is another one, though human exposure is generally skin or indirect contact. Boric Acid, one of the chemical components of Borax, is toxic in both acute exposure (LF50 = 1-20g/kg in humans, depending on age), and chronic exposure (as little as 32mg/kg for chronic lethal dose). However, Borax, itself, is a salt of Boric Acid, and so, doesn't carry the same toxicity unless broken down with something like hydrochloric acid. In fact, Borax is a great detergent for all sorts of household cleaning purposes (laundry, dishes, all-purpose cleaning).
Baking soda (sodium bicarbonate) -- most commonly used as a leavening agent in baked goods -- is the product of a reaction of sodium chloride, ammonia, and carbon dioxide in water. Its cousin, washing soda (sodium carbonate) can be produced using sodium hydroxide. Which one you get from that initial reaction depends on how much carbon dioxide you add to the mix.