You can go without food for quite a while if you have to. Going without water is much
We normally lose water from our bodies in many ways, including sweating, water
contained in the air we exhale (which contains mush more water than the air we inhale,
because of evaporation from the lungs and mucous membranes), urine, and water in the
stool. To make up for this, we need to take in water constantly to make up for the losses,
usually by drinking.
We also produce urine constantly, not only to get rid of excess water but also to flush out
various chemicals we don't need any more. (Essentially, the kidneys are chemical filters
for your blood.) Since the flushing process requires water, you need to produce at least a
little urine all the time. The amount of water in the urine varies depending on whether
your body needs to save or get rid of water, but we have to have some water in the urine.
Infants produce more urine than older children and adults because their kidneys aren't
fully mature and can't save as much water as they can when they're older.
There are several ways to decide whether someone is becoming "dehydrated", or taking
in less water than they are putting out. Dry mucous membranes in the mouth, sunken
eyes, and (in babies) sunken fontanelles (the "soft spot" on the head), are all signs of
dehydration. A more dependable sign, especially since it appears sooner than these
symptoms, is a drop in urine output. Normally a child should urinate at least every 6
hours; smaller children probably urinate more often, but 6 hours is the minimum beyond
which treatment may be needed. Another sign of dehydration is weight loss over days or
hours. Slow weight changes are usually dietary (or due to chronic illness); quick weight
loss is usually because of dehydration, and is not good for you even if you're trying to
What causes gastroenteritis?
The most common reason for gastroenteritis in young children is viral. There are many
viruses that can produce diarrhea, with or without vomiting. Among these are the
rotaviruses, which usually appear in the community in wintertime, the enteroviruses,
which are more common in summer, and adenoviruses, which can occur year-round but
usually cause respiratory problems, although they can cause diarrhea in babies.
Generally, once a particular virus infects you, you aren't likely to get it again; however,
there are many viruses around and it takes a while for a person to have all of them. Also
viruses can mutate (change some of their characteristics) and may be able to infect people
who are immune to the "original" form. This kind of change is the reason we need
influenza vaccine every year: this year's influenza is almost always a new and improved
(from the virus' standpoint) version, and we need new and improved vaccines to help
There are also bacteria that cause gastroenteritis. They aren't as common in the United
States and other countries with well-developed plumbing and sanitation systems, but they
are seen frequently where sanitation isn't as good. They can also come from contaminated
food (for example, Salmonella outbreaks in potato salad or other egg-based dishes, or E.
coliO157 in some undercooked meat). Bacterial gastroenteritis is rarer than viral, but if
often won't go away without antibiotics. Often, if we aren't sure that a child has a viral
infection, we will try to culture stool samples to see if pathogenic ("bad") bacteria are
present. If we find a bacterial cause, the culture results will also help us choose a good
antibiotic to treat the infection.
Although we're discussing infectious gastroenteritis in this Web page, I should also
mention one "chemical" cause of diarrhea: lactose intolerance. Many people just can't
digest lactose (milk sugar) no matter what, unless they take supplementary enzymes to
help with digestion or bacteria which are normally harmless but help break the lactose
down so the body can finish the process. For a long time we thought that it's very
common in viral gastroenteritis to lose your ability to digest lactose for a few days until
the infected mucous membrane cells are replaced (you normally grow new mucous
membranes every 3 days or so). Drinking milk or eating milk-based foods while you can't
digest lactose may cause or worsen diarrhea. This doesn't happen in all patients, though,
and most doctors now recommend letting your child continue to drink milk and milk-
based formulas even with diarrhea -- especially if milk or formula is all your child will
drink. Breast milk in particular seems to help children with gastroenteritis, although that
may be because of its many other "ingredients" -- including mother's antibodies to many
viruses, possibly including the virus that's making the baby sick. Soy formulas do not
contain lactose, and some doctors may recommend switching to a soy formula
temporarily during a bout of gastroenteritis. (Besides, soy formulas tend to constipate
some children, which may also help the diarrhea.)
Although bacterial gastroenteritis is helped by antibiotics, they don't help in cases of the
more common viral gastroenteritis -- in fact, antibiotics can cause or worsen diarrhea.
Usually we try to make sure a child stays properly hydrated, and wait until the virus has
run its course.
Keeping your child well-hydrated is the mainstay of getting him or her over
gastroenteritis. We described how to tell if someone is dehydrated above. The important
part of treatment is to give fluids that your child will keep down and absorb.
Pedialyte TM and similar "rehydration formulas" consist of water with sugar and certain
minerals. The sugar not only provides energy, but with the minerals helps the body
absorb water better. Unfortunately Pedialyte doesn't taste all that good (I didn't think
much of it when I tried it, and most children I know agree.) There are flavoured versions
available, but sometimes they aren't all that great-tasting either. Other brands of
rehydration fluids (Infalyte, Rehydralyte) may taste better to some people; they certainly
taste different. Altough we have occasionally recommended boiling rice in water, pouring
off the water, and serving that to a child with gastroenteritis, we no longer recommend
that; there aren't enough minerals or carbohydrates in the rice water for it to be well-
absorbed. Giving rice in the cooking water, however, does seem to help out a lot.
Many of us have tried to get children to drink Pedialyte by mixing it with other things.
The risk here is that changing the sugar/mineral balance will make the fluids harder to
absorb. Unsweetened Kool-Aid is fairly safe, since it contains no sugar. Although I've
tried it in desperation myself, I do not recommend mixing soda pop into Pedialyte if you
can avoid it. The sugar concentration of, for example, PepsiCola will throw the Pedialyte
balance way off -- and, in fact, there is so much sugar in most soft drinks that they can act
as laxatives and worsen diarrhea. The same holds true for "sports drinks" such as
Gatorade. (I haven't tried mixing diet soda and Pedialyte; that should be all right but
might cause problems.)
Another fluid you should avoid with severe gastroenteritis is plain water in large
amounts. Plain water is not absorbed as well as water with sugar and minerals. More
important, since you lose minerals as well as water in diarrhea and plain water doesn't
make up for the minerals lost, your mineral balances can be thrown way off -- possibly to
the point of having seizures.
If your child is vomiting persistently, it's best not to push fluids very hard -- the results
can be frustrating (and a mess) for all concerned. I like to treat vomiting by waiting about
10-15 minutes after the last feeding attempt, then giving a very small amount of clear
liquid (as little as a teaspoon). If this stays down, then give another tablespoon 2-3
minutes later. If that stays down also, then increase the next feeding by 1 teaspoon, and
keep increasing the amount until you are giving 2-4 ounces/feeding (depending on your
child's size). If your child throws up a feeding, wait 15-30 minutes, then resume at one
teaspoon per feeding and work up again. Again, watch the urine output -- that's the best
indicator of whether you're getting enough fluid in.
As we all know, stool consistency depends largely on what kinds of food we eat even
under normal circumstances. Eating the right kinds of foods and avoiding the wrong ones
can make a big difference in how fast you get over gastroenteritis.
Usually clear liquids are the most easily absorbed food of all. They also provide extra
water (along with minerals) to help prevent dehydration, and they are usually well-
tolerated. The best clear liquid is Pedialyte (if your child will actually drink it -- see
above). Clear soups (like bouillon) don't work well, because they are often very salty.
Tea, even with a little sugar, is actually not very good, since the caffeine in tea is a
diuretic (it makes you urinate more -- which you don't want if you're becoming
dehydrated). Heavily sugared drinks, like cola, can actually increase diarrhea by drawing
water into the stool (we often recommend corn syrup added to formula as a gentle
treatment for constipated babies for the same reason). Once your child's appetite begins
to improve, start giving foods again.
As you may find in other discussions in my Office on the Web, I'm a minimalist when it
comes to throwing medicines of any sort at sick children. This is especially true with
gastroenteritis. The diarrhea will usually go away in a few days without medicines if you
avoid irritating food, especially milk. Over-the-counter diarrhea remedies tend to stop the
diarrhea without doing anything about the cause. (Remember that we have almost no
antibiotics for viruses.) If the problem is a bacterial infection, antibiotics may help, but
we have to know what bacteria we're dealing with to pick the right antibiotics. Remember
antibiotics, by changing the bacterial population in the intestines, can cause diarrhea
themselves. And most of the antidiarrhea medicines have side effects -- some of which
can be really nasty. In some rare cases antidiarrhea medicines may help, but you should
ask your doctor before trying any of them.
When to call for help
If your child hasn't urinated for 6 hours or more and you can't get him/her to take
or keep even clear liquids down
If your child is becoming lethargic or listless. ("Lethargic" means that your child
is so out of it that s/he can't recognize people s/he usually knows. A child that
can't recognize his/her parents is very lethargic and needs to be seen by a doctor.
A "listless" child is one who isn't as active and playful as usual: the less active,
the more listless.)
If your child's mouth looks dry or his/her eyes are sunken (these are late signs of
dehydration, although usually not as late as true lethargy.)
Often we can suggest other measures that you can try at home, many of which I've listed
above. We may suggest that you take your child to an after-hours clinic or emergency
room where a doctor can examine and if needed give fluids IV. (In some bad cases of
gastroenteritis the best way to help get a child over the worst part is to give them constant
IV fluids until the vomiting and diarrhea go away -- which can sometimes take a couple
of days if there's a bad infection involved.)