Can You Suddenly Become Lactose Intolerant?

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Have you always enjoyed dairy products but recently noticed that you’re experiencing some symptoms of lactose intolerance after eating your favorite chocolate candy, cheese or milk?

Our bodies are complex and it’s often difficult to assess what is going on inside. Lactose intolerance is no exception when it comes to complexity.

It can be a confusing condition. Is it genetic or can you suddenly become lactose intolerant? It’s actually both.

It’s possible to suddenly develop lactose intolerance from four sources: primary, congenital, developmental, and secondary. Primary and congenital are due to genetics and biological reasons. Developmental and secondary are developed mainly from medical conditions and medications.

Let’s look at how you can suddenly become lactose intolerant in more detail.

First Things First: What Is Lactose Intolerance Exactly?

Often known as lactose malabsorption, being lactose intolerant means your body is unable to digest lactose. Lactose is the naturally occurring sugar found in dairy products such as cheese, milk and yogurt. 

It affects around 36% of Americans and the condition is incurable. That doesn’t mean however, that you can’t manage it. 

What Are The Symptoms Of Lactose Intolerance?

Specific symptoms can vary from person to person, but the most common of the symptoms include:

  • Flatulence 
  • Diarrhea 
  • Stomach cramps
  • Tightness in the abdomen 
  • Abdominal pain
  • Indigestion 
  • Burping 
  • Nausea and vomiting 

A Brief History: Humans and Lactose 

It is interesting to know when we examine lactose intolerance, the brief history of humans and lactose. We were never really meant to consume lactose into adulthood.

When we are babies, we create an enzyme called lactase which assists us in digesting our mother’s milk. 

When we grow up, this enzyme stops being produced – at least it should. When European farmers first began drinking milk around 10,000 years ago, they probably felt sick and flatulent.

However, over time – we have evolved to continue tolerating lactose through a DNA mutation. Seemingly though, some people do not share this trait of lactase persistence.

There isn’t any conclusive evidence as to why – but many historians and scientists suggest it is down to geographical and cultural factors. 

The Chinese, for example, hardly consume milk or other dairy products at all, and it’s reported that it makes many Chinese people sick.

Potentially, their culture did not introduce milk into their adult lives and thus, might not have the DNA mutation that many Europeans and North Americans might have. 

Can You Suddenly Develop Lactose Intolerance?

The short answer is yes. However, it’s not as simple as that. The four main kinds of lactose intolerance development are primary, congenital, developmental and secondary.

Congenital and primary are inherited intolerances to lactose. The most common intolerance is primary and since it is inherited, there is little you can do about it. The same applies to congenital lactose intolerance.

The difference between the two though, is that primary intolerance symptoms do not usually become apparent for a few years, whereas with congenital intolerance, a gene is passed from both parents, and it is immediately obvious. 

Developmental intolerance can generally be short term and normally found in children that were born prematurely – this is because their body has not developed enough to produce enough lactase.  It can carry on into later life though. 

If you have a problem with your small intestine, it is possible to develop secondary lactose intolerance. This doesn’t have a particular age limit and can happen to anybody.

The normal factors in secondary lactose intolerance are Crohn’s disease, Celiac disease, infectious gastroenteritis, ulcerative colitis or certain medications such as chemotherapy drugs and antibiotics. 

It is the problem with the small intestine that gives people the symptoms we mentioned earlier.

When the body cannot digest the lactose sugar, the colon bacteria begin to ferment the lactose and this results in excessive gas and water.

The condition is chronic and it is entirely possible to develop it out of nowhere, if you have another condition that prompts it.

As we age or avoid dairy for whatever reason, our bodies might develop an intolerance for dairy too, which is also known as acquired lactase deficiency. 

Lactose Intolerance Diagnosis 

It can be difficult for us to diagnose lactose intolerance ourselves because many of the symptoms mirror that of IBS or even an allergic reaction to milk. 

If you’re able to see a gastroenterologist, you may be offered a lactose breath test which will analyze your hydrogen levels after consuming dairy. The gas (hydrogen) is a product of undigested lactose.

Often, the diagnosis is established based on the patient’s history.  If lactose consumption produces symptoms like gas, bloating, and diarrhea, and elimination of dairy eliminates these symptoms, the diagnosis is fairly well established.  To confirm, lactose can be reintroduced to see if symptoms recur.


The best thing you can do if you are lactose intolerant is to stay clear of food and drink that has lactose in it. These can include: 

  • Cheese 
  • Milk
  • Candy bars (containing chocolate)
  • Yogurts
  • Cream
  • Ice cream
  • Some processed foods 
  • Salad dressing 
  • Mayonnaise 

Instead, look at the labels for lactose free products. Many dairy products have lactose free options available or you could choose to make it yourself at home.

Perhaps you could try Greek yogurt that’s low in lactose and free of whey to make some of your favorite things. Greek yogurt is more well tolerated than other dairy products.

There are over the counter options to consider such as Lactaid which can help the body process lactose more efficiently. 

Managing the symptoms of lactose intolerance will feel like a drag sometimes but think of it as part of your normal routine. Over time, it will become second nature. 

Sudden Lactose Intolerance Final Thoughts

Is it possible to develop sudden lactose intolerance? Yes, assuming there was an underlying condition. 

Can you develop lactose intolerance over time? Yes, in many ways. 

Lactose intolerance is quite common and is not typically a serious concern, but can cause inconvenient and bothersome symptoms.

However, if you notice any extreme changes in your digestive health, it is imperative that you see your doctor about the sudden change in symptoms.

Learn more about lactose intolerance in these articles:

Written and Medically Reviewed By

  • Chelsea Cleary, RDN

    Chelsea is a Registered Dietitian Nutritionist (RDN) specializing in holistic treatment for chronic digestive disorders such as Irritable Bowel Syndrome (IBS), SIBO, and Crohn’s disease. She educates patients on how they can heal themselves from their conditions by modifying lifestyle and dietary habits.

  • Julie Guider, M.D.

    Dr. Julie Guider earned her medical degree from Louisiana State University School of Medicine. She completed residency in internal medicine at the University of Virginia. She completed her general gastroenterology and advanced endoscopy fellowships at University of Texas-Houston. She is a member of several national GI societies including the AGA, ACG, and ASGE as well as state and local medical societies.