Given that cheese is one of the few truly great things in this world, it's safe to say some people completely ignore their signs of lactose intolerance so they can keep eating pizza with wild abandon. (Totally understandable.) Although it affects up to 65 percent of the population, not everyone has a clear picture of what lactose intolerance means, partly because it can manifest differently depending on the severity.

One common misconception is that lactose intolerance is a dairy allergy, but that's actually not the case. Food allergies are a totally different ballgame than food intolerances; allergies mean your body's immune system treats a specific food as an invader, and this reaction can be life-threatening. Intolerances, on the other hand, refer to a difficulty digesting certain kinds of food — the reaction can be unpleasant, but it's not going to seriously harm you. So lactose intolerance and a dairy allergy are two separate things.

Naturally, this brings up the question of what lactose intolerance means. According to the Mayo Clinic website, it occurs "when your small intestine doesn't produce enough of an enzyme (lactase) to digest milk sugar (lactose)." When you consume dairy, your body uses lactase to break down milk sugar into glucose and galactose, which are then absorbed through your intestines into your bloodstream. If you don't have enough lactase in your system, though, the lactose continues on its merry way into the colon, and you start to run into problems.

There are three main kinds of lactose intolerance: primary, secondary, and congenital. Primary means your lactase production decreased with age, and it's the most common. Secondary is a lactase deficiency caused by a problem with your small intestine. The rarest, congenital lactose intolerance, occurs when a baby is born with little to no lactase production.

So what are the signs of lactose intolerance? Here's a look below.