Acid is produced by stomach. It is mild 0.5% HCL. It plays two important roles like:
1. It initiates protein digestion by activating the conversion of pepsinogen to pepsin.
2. It provides acidic medium for the activity of pepsin and other enzymes present in gastric juice.
However, if the level of this HCl exceeds its normal levels, it results in acidity/acid reflux, burning sensation in the throat and heart, headache, vomiting, rashes on skin etc. Exposure to higher levels of HCl for longer durations can also result in the development of peptic ulcers/ulcers in the stomach.