Lactic Acid is NOT a waste product and can do absolutely nothing to harm you.
'In fact, lactate may be one of the most important energy fuels in the body. Let us banish once and for all the bad publicity that lactic acid has attracted for so long and elevate it to its rightful place as one of the most important of the body’s fuels’ Tim Noakes
Crucially, lactate actually helps to produce energy. It is created during glycolysis, which literally means the breakdown of glucose. Glucose is derived from the carbohydrate we eat, and glycolysis kick starts chemical processes within our muscles that produce the energy required for sustained muscular contraction. Without glycolysis we would be unable to sustain exercise for more than a few seconds.
Lactic acid, like lactate, is not a waste product. During recovery, when there is a much more plentiful supply of oxygen, lactic acid looses its two hydrogens and reverts to pyruvic acid for use as an energy source. In fact 50% of the lactate produced during a tough workout (remember that lactic acid returns to lactate when it enters the blood stream) is used for replenishing muscle glycogen stores during recovery.