Speaking of acids, what acid in the stomach breaks down protein into amino acids that can be absorbed in the small intestine? You got it! Hydrochloric acid. Don't try putting it on the outside of your body; it will break that down too. What acid does your muscles produce during anaerobic exercise (that's when you don't have enough oxygen in your blood stream to pay for the energy produced)? That would be lactic acid which some say can leave a feeling of soreness if you don't cool down and stretch or massage the muscles used. You will pay that oxygen debt shortly after you stop the exercise.
Some good bacteria that work anaerobically metabolizing glycogen in the vagina also produce lactic acid which protects the vagina from yeast infections, among other things. A dangerous acid is acid rain which kills vegetation. It is produced by burning coal containing sulfur. A large amount of energy in our country is produced by burning coal. If there’s sulfur in the coal, it goes up in the smoke cloud, mixes with water, and rains down as sulfuric acid. Not a fun sequence of events. Another reason to put more effort into solar energy cells, wind and wave generated