Also, if you were stung by a Man o’ War, vinegar will make their stings worse, so don’t use it in this case, instead, use the next solution.If no vinegar is available, rinsing the sting in a baking soda / sea water (only if it’s salt water, no fresh water) mixture and then gently apply a baking soda / sea water paste to the area should also neutralize the nematocysts. If baking soda isn’t available, rinsing with sea water works too, just not as well.Next, use a knife, shaving razor, credit card, etc. to very gently “shave” the area stung (don’t use very much pressure or it may cause any non-neutralized nematocysts to fire) to get rid of any remaining nematocysts. Some guides also recommend gently applying shaving cream or soap lather before shaving the nematocysts off.