-It won't create any problems re: water, etc.
-Use as a last resort if rest doesn't work, because if shots are taken multiple times the body builds up a tolerance and the shots lose their effectiveness.
-They work like magic to get rid of pain..HOWEVER consider yourself lucky to fix the problem then figure out what caused the injury in the first place and avoid it, otherwise the equation will stay the same and the same injury could come back again, be harder to fix a second time. Therefore, change the exercise or reduce the weight and increase the reps, in addition to better more thorough warm ups and reduced rest time between sets that keep the area warm.