The Merriam-Webster Online dictionary has this to say about the origin of the interjection "ouch" — Etymology: origin unknown. Appropriate, since we often are not exactly sure what has caused (or is impolitely continuing to cause) pain to our fine form. What we are sure about is that we want the ouch to go away quickly and completely so that we may return to our happy lives.

Enter your friend and mine — pain killers. Modern science has moved us away from chewing on sweet birch or white willow bark to extract the natural salicylic acid (aka — aspirin), providing a wide assortment of substances that will do the trick.

Low carb lifestylers often become overly familiar with pain killers as they begin or increase their fitness routines (you are working out — pumping iron and revving the heart — aren't you?) With this zeal for exercise, unintentional insult to the body can sometimes occur and we reach for our medicine cabinet's blessed bottle of relief to stop that pain nonsense. However, each discomfort destroyer works a different way and may or may not suit your personal ouchie. Let's take a closer look at the main players, shall we?

Aspirin (such as Bayer)

We start life's ouch-away path with orange-colored baby aspirin and many stay that course throughout adulthood. And why not? Aspirin was one of the first basic pain remedies synthesized in the lab after millennia of natural healers prescribed the consumption of plants that contained high levels of salicylic acid to their patients. Actually, a large variety of herbs, spices, fruits and vegetables contain salicylic acid and this is one of the suspected reasons vegetarians have lower incidences of heart attacks.

One of the ways that salicylic acid helps with ouchies and with heart attacks is that it is an anti-inflammatory: retards and reduces swelling. Swelling in arterial walls is not a good thing for heart function and swelling due to injuries presses on nerves and makes us say, "Stop that! It hurts. Right now! I mean it!"

Inflammation due to injury stems from injured blood and lymphatic vessels leaking fluids into the surrounding tissue, but also from the body sending fluid that is laden with healing helpers. That part is nice, but it still hurts and the pressure due to the swelling can further injure nearby tissue. This will not do.

Aspirin also works as a pain-reliever by inhibiting the synthesis of prostaglandins. No, these are not related to the prostate. Prostaglandins, among other things, activate and stimulate pain responses in the body. They also promote that disrespectful inflammation we talked about earlier. Why does the body do something so, well, hurtful? Well, pain is actually a survival response. Mongo say ouch - Mongo got big hurt — Mongo must stop big hurt — Mongo fix problem…in other words, if Mongo wasn't unhappy, he might neither notice nor care about the situation. The infection goes unchecked; the injured foot goes untreated, etc. Mongo get worse, Mongo get more worse, Mongo push up daisies. But, once the pain has your attention and you know where and what to work on, there is really no reason to keep it around and pain relievers accomplish this for us.

What else can aspirin do for our ouchies? Well, aspirin is also an anti-pyretic. It reduces fever. Who causes that? Those wacky prostaglandins! Fevers help to kill foreign invaders such as parasites and bacteria and also increase the production, response time and killing capacity of white blood cells. Further, other immune functions work better at elevated temperatures. So, like pain, fever is actually a good thing, albeit not the most comfortable state of affairs. And, the immune system will do its work at normal body temperature, just a tad more lethargically.

So, aspirin is anti-inflammatory, anti-pyretic and acts as a pain reliever. Why use anything else? Well, aspirin can cause stomach upset. Also, aspirin acts as an anti-coagulant. Great if you had a heart attack and clot formation would make the situation worse, but bad if you have a bleeding injury. Aspirin has been shown to promote a potentially deadly condition called Reye syndrome in children suffering from viral illnesses. Lastly, aspirin changes the way your kidneys make urine, in some rare cases produces difficulty with breathing and is dangerous in high doses.

Acetaminophen (such as Tylenol)

Acetaminophen has both pain reliving and fever-reducing properties. It reduces pain by blocking the production of prostaglandins. The brain doesn't get the signals that say ouch and your tolerance for those aches and ow's goes up. Fever reduction is accomplished through a stern chat with the brain's heat-regulating center. However, acetaminophen does not have aspirin's anti-inflammatory properties — it is not the drug of choice if you have swelling you need to control. But, you don't have to worry about any blood-clotting problems with acetaminophen. A bleeding cut will clot up nicely if you use acetaminophen. Also, it is rare for acetaminophen to add a tummy-ache to your current level of annoyance. The downsides? Overdose or prolonged use can cause liver problems, kidney problems and/or anemia in some folks and it is fairly easy, surprisingly, to overdose on acetaminophen. Just 5x the maximum daily adult dose for extra-strength formulations can be life-threatening. 2x the maximum daily adult dose for extra-strength can be as dangerous for children. Moreover, many formulations contain aspartame, so they should not be given to people, especially children, with phenylketonuria. However, unlike aspirin, acetaminophen has not been implicated in Reye Syndrome, so is safe for youngsters with viral illnesses.

Ibuprofen (such as Advil)

Ibuprofen belongs to a class of compounds with the eye-watering name of non-steroidal anti-inflammatory drugs or NSAIDS. They work by blocking the enzyme that makes your friend and mine — the prostaglandins. Lower doses of ibuprofen are fine pain relievers and higher doses are anti-inflammatory. Ibuprofen also reduces fever. Actually, ibuprofen works much like aspirin in most aspects. This means, though, that it does have aspirin's anti-clotting effects and can promote tummy troubles. However, the tummy turbulence is neither as common nor as intense as for aspirin. Overdosing can cause liver problems, some central nervous system conditions, stomach ulceration, kidney impairment and allergic symptoms such as rashes. Also, NSAIDS are excreted in breast milk, so nursing mothers should avoid such until Junior can munch Atkins Bars.

Naproxen (such as Aleve)

A relative newbie for our medicine cabinet arsenal (FDA approved only in 1991), this is another example of NSAIDS at work. Re-read the above paragraph and you have the story for naproxen.

So you leap on that treadmill with the fire of fitness burning in your soul and limp off in the direction of your first aid kit. Which of the usual suspects do you grab? If you have swelling, aspirin, ibuprofen or naproxen are the choices. Aspirin works better as an inflammatory for most people, but NSAIDS seem to be easier on the stomach. Aspirin is also cheaper. However, do not take aspirin or NSAIDS before a workout. The anti-clotting properties of these fellows has been linked to internal bleeding when taken before running and any high-intensity routine should likely not be introduced with these pain pummelers (what are you doing working out with an injury anyway, hmmm….). If swelling is not an issue, acetaminophen is back in the picture and it is many doctor's choice for people who are allergic to aspirin, are prone to stomach troubles or have bleeding ulcers/blood clotting disorders. But, watch for products with aspartame if you have phenylketonuria or avoid aspartame on general principle. Nursing mothers should avoid NSAIDS. To prevent accidentally administering it to kids with chicken pox or other viral maladies, households with small children should likely not stock aspirin.

For all — READ THE LABELS!!! A quick perusal of the labels for the major name brands finds the Evil Ose Squad (dextrose, lactose, sucrose, etc.) and various members of the Sneaky Starch Clan (corn starch, modified food starch, vegetable starch) running rampant. Manufacturers do not always have low carbers' interests at heart. However, you can find brands — both name and generic — that are more low carb friendly. I know that the mass of one tablet or caplet is not large in a dietary sense, but take a couple at a time (and who doesn't), several times a day for several days, and you could be experiencing carb creep with actual impact on your form. You don't need that added to your week's list of woes!

Activity. Combined with a low carb lifestyle, this is a golden road to health and wellness for many of us. But, when your ankle is twisted in a pothole, be ready with the appropriate anti-ouchie. Don't forget to follow the RICE regimen (rest-ice-compression-elevation) and don't hesitate to see a doctor if you are truly worried. Minimize the time for healing by taking the appropriate steps!