Saline solution containing 0.9% sodium chloride is isotonic and makes a very good antiseptic. You need to add roughly 1 tsp of salt to ½ litre of cooled, boiled water; it is best used when tepid.
Salted water (saline) is highly recommended for washing wounds, flushing out nasal cavities (this has been used in Yoga for centuries and is said to help in the treatment of asthma and sinusitis), and as an eye wash.
A handful of salt added to a bath used to be the suggested treatment for bathing leg ulcers, post-operative wounds and after childbirth. Unfortunately many hospitals seem to have forgotten this in favour of expensive, and possibly harmful, antibiotic salves and lotions.