You feel nauseous after eating dairy
There are different degrees of lactose intolerance, according to Chicago-based registered dietitian Karen Raden, RD; some individuals experience more extreme symptoms than others. In the worst cases, a lactase deficiency can cause someone to feel the need to vomit shortly after they consume a dairy product. “Gas in the intestine inflates it like a balloon, inducing a vomiting response,” says Dr. Mason. This . is relatively rare, according to Raden, but if it’s regularly occurring to you when you eat milk products, it’s probably a sign of a lactase deficiency.
Your belly is in pain, and making sounds
Without lactase, your body’s attempt at breaking down lactose . itself can draw a lot of water into your intestine, in addition to gas in your gut. The result is an unfortunate combination of diarrhea, cramps, and the sound of gurgling or rumbling in the belly, also known as borborygmi. According to eMedicineHealth.com, sometimes the diarrhea of someone who is lactose intolerant will also appear foamy, the result of all of the extra gas and fluid sloshing around in the gut.
You regularly experience bloating and gas
You know pretty quickly when the frozen yogurt you ate an hour ago isn’t digesting correctly; you’ll feel it in your puffed-out abdomen. Joel B. Mason, MD, a professor of medicine and nutrition at Tufts University, says all of these symptoms can be the result of a deficiency of the enzyme lactase, which typically breaks down the two types of sugar in each lactose molecule so they can be easily absorbed into the intestine. Without lactase, lactose molecules will travel down the intestinal track whole and bacteria will try to break them down through a process of fermentation, which produces a whole lot of extra gas in your abdomen.