Because of spam, I personally moderate all comments left on my blog. That means you will not see your comment when you post it. It will instead show up within 48 hours, along with my response if one is appropriate.

All comments are welcome and will be posted, even if they are negative. You just can't promote other sites or products in them.

If you have a personal question about LI or any related topic you can send me an email at

Otherwise, this blog and my Lactose Intolerance Clearinghouse are now legacy sites, meaning that I am not updating them any longer. The basic information about LI is still sound. However, product information and weblinks may be out of date.

My old website can be found at

For quick offline reference, you can purchase Planet Lactose: The Best of the Blog as an ebook on or or or a whole lot of other places that Smashwords is suppose to distribute the book to. Almost 100,000 words on LI, allergies, milk products, milk-free products, and the genetics of intolerance, along with large helpings of the weirdness that is the Net.

Sunday, April 26, 2009

How Long Does a Lactose Attack Last?

I hate getting questions that I can't answer, but "it depends" is all-too-often the only real comment that I can make.

This was in an email I recently received:

After reading pretty much everything on your website and a lot of others, I still haven't found the answer to this question: How long after you stop consuming lactose does it clear your system and stop causing symptoms? Are there any residual effects and/or damage to the gut?

There is very little that's more individual than a lactose attack. It varies not just by person to person, but every single time you take in more lactose than you can digest. How much lactose you eat, whether it's part of a meal or whether it's mostly liquid, how much lactase may remain in your system, and how sensitive your intestines are all play a major role.

The symptoms may be mild or severe and may last for a short time or for quite a while.

You cannot damage the gut by having lactose. If you are particularly sensitive or also have Irritable Bowel Syndrome, your intestines may keep on spasming even after the lactose is gone. At that point taking an antidiarrheal drug to stop the spasming is a good idea. Don't take one right away thinking that you're stopping the symptoms. You'd just be keeping the lactose in you longer.

Extreme cases of lactose intolerance (LI), meaning times when someone keeps having milk despite the symptoms, can lead to dehydration from the water loss. That used to happen in the days before people knew what LI was. (If you didn't know that milk caused your problem you wouldn't think to stop having it.) I haven't heard of a case of dehydration in a very long time. Knowing all about LI is far too common in the U.S. This might be a concern in some other countries where understanding of LI is just beginning to reach our levels.

LI is uncomfortable but not dangerous. The sympotms will go away when the lactose is gone (and you make sure not take in more lactose). It just seems like forever.

Bookmark and Share


mgloberman said...

Re: How long an episode lasts. I have experienced extreem discomfort for over two days. I found that taking a product like Imodium will give substantial relief within an hour!!

I also found that you can not generalize about foods. For example, I can eat a well aged (hard yellow) cheese such as Swiss, mozzarella etc. without any reaction. But a similar named cheese that is softer, creamier ,and not as yellow that has not been aged as long will cause distress!
Hope this helps someone -- mel Globerman, Lake Worth, FL.

Anonymous said...

FYI mozzarella is only aged for about 30 days and quite often causes problems for those that are LI.

Very hard aged cheeses such as parmesan, romano and cheddar contain much less lactose and are less likely to cause a problem.

Anonymous said...

I had shared a small shake and have been having nausea for the past two days. How long would it last? Or is there anything I should do? Also I've been vomiting.

Anonymous said...

I am suffering from the effects of a 4 oz. milk shake now for the third day. The first night I had diarriah thru the night and threw up twice. I also had very uncomfortable stomach cramps. I am very worried that these symptoms will last for months like my first bout with lactose intolerance. Which lasted several months. Besides staying away from lactose is there anything else I can do to feel better. I honestly thought I wouldn't have any reaction when I drank the milk shake, because I have been feeling so good. Right now, even tho I'm staying away from lactose entirely, I am still quite sick.
Thank you for any help.

Christina said...

As a severely lactose intolerant individual, the only thing I can have is aged Sheeps cheese. Cheese aged over 12 months or more is lactose free. I go for the two year reserve stuff and even then, just a little and not too often.

Unknown said...

Why do some things affect me more than others? I can occasionally drink milk with only mild cramps and gas, cheese doesn't bother me much, yogurt doesn't really bother me, but ice cream used to bother me so bad I'd have to go to the hospital. I haven't ate ice cream in a while but the last time I had it these symptoms didn't occur.why does it only happen sometimes,worse with some dairy products,and different severities?

Anonymous said...

Sucrose in particular (sugar) seems to aggravate symptoms of intestinal sensitivity for some. (Check out the "Specific Carbohydrate
Diet"for more information)

Monique said...

Do you have a milk allergy? Those symptoms are more severe... Sounds more like what you described!,

DEL said...

Thanks Mel.

Anonymous said...

I'm currently having a lactose intolerance attack right now, due to having forgotten to take my digestive enzymes before downing my glass of milk. I finally remembered my enzymes, so my tummy trouble would dissipate in under an hour. A general digestive enzymes capsules or liquid usually allows me to consume milk without the trouble, when I dont forget to take it along with my milk. But times like this, even if taken late, it still works at halting my raging belly. The enzyme lactase is what digest the lactose in milk, and there are supplements available that contain just lactase, and no other enzymes. I personally keep a broad spectrum enzyme supplement, because I have other issues besides just lactose. But, whichever of the two kinds, they both work for lactose intolerance, as long as lactase is one of it's major enzymes.

Anonymous said...


Most people who are lactose intolerant can consume A2 milk without any problem. Yes, there is an A2 Brand of milk, but I'm talking A2 as the A2 type of milk, not the brand... although, the brand itself is 100% A2 type. Many health food stores in the US and Australia carry A2 type milk. The normal grocery store milk we consume is A1 type of milk. A1 is produced by cows that are newer breeds, that are genetically designed in the last few centuries. A2 type milk is produced by the original, unmodified breeds of cows. Breeds that have been existing as they are for thousands of years.

Anonymous said...

Hi, I think it could be worth speaking to your doctor about having IBS or being celiac, I am celiac but over time gluten effects the villi in your digestive system and after time you can develop LI, yet excluding gluten wheat and barley from your diet

Anonymous said...

If you are lactose intolerant, shakes won't make you throw up. It will however make you go to the bathroom. Someone must have made it wrong, or if there was whipped cream in it, they could have left it out all day. You may have caught a bug.

Xavier said...

Hi, I've been diagnosed with LI a year ago and still try hard to find a balance between enzymes intake when I eat dairy and find it really hard to gauge. The only symptom I ever get is very sharp pain on the bottom left part of my abdomen (that is the descending colon). Each time I have an attack, it will happen at least 24 hours after the intake and lasts between 3 hours to 48 hours. I manage the pain with ibuprofen and acetaminophen. As soon as I get pain onset, very mild pain, I take medication and it sometimes help prevents the pain from worsening. Then I tell myself that it is my own fault that I am suffering, because I could not resist having a little cheese and believed that the enzymes pills would prevent issues...not always!

Jen Ward said...

How do they test for it and how long does it take to get the result?

Steve Carper said...

Jen, Undigested lactose in the body is fermented by bacteria in the large intestine. This produces hydrogen as a by-product. The hydrogen goes through the blood stream and is exhaled in the breath. Nothing else does this so if a breath test measures hydrogen then undigested lactose is the cause. The standard test involves drinking lactose dissolved in a glass of water. You need to fast for 12 hours before the test, so that the liquid will go quickly through the intestines and other food will be out of the way. The technician will have you blow up a small bag every 15 minutes for about two hours. The bags are sent in for analysis. How long it takes for results depends on your medical system. My system wouldn't be more than a day or two, but I don't know about yours.

It's possible that you might be asked to be a blood test instead of a breath test. Digested lactose will raise the glucose sugar level in your blood; undigested lactose will not. After drinking the lactose, a small vial of blood is drawn at intervals. These are tested like any other blood sample and should take the same amount of time.

Unknown said...

Get checked for giardia parisites. They have same symptoms.

Felicity Bro said...

For me I have had a lactose episode for almost two weeks it all depends how your bowel movements are and how much lactose you have had would say give it a week if it still will not go away consult a doctor

Unknown said...

I had two bowls of ice cream yesterday before my mom told me I must be lactose intolerant. I throw up once. My stomach is killing me. But barely any poop will come out so im not having diarrhea. When will the pain go away?

Steve Carper said...

It's possible to have an attack of LI without diarrhea but not likely. In order to understand the cause you have to look at what you could eat without problems. If you've had small amounts of dairy products with no symptoms, then two bowls of ice cream may have just overwhelmed your system. Someone who is only mildly LI can eat some dairy but not large quantities.

If this is the first time two bowls of ice cream or any other large amount of dairy have affected you, then something else might be the cause. Lots of ailments can produce vomiting.

In any event, stick to smaller amounts of dairy. If even those affect you then you should seriously think of avoiding all dairy products, except those that are made lactose-free. Lactaid and others make lactose-free ice cream. If you try them and still get sick then something else in the milk is the probable cause.