Cyclical vomiting syndrome

Cyclical vomiting syndrome (CVS) is a rare vomiting disorder most commonly seen in children, although it can affect adults too.

Someone with CVS will frequently feel very sick and will vomit for hours, or even days, at a time.

They will then recover from the episode and feel perfectly well, before experiencing another episode perhaps a month or so later. 

These vomiting attacks are not explained by an infection or other illness.

CVS can affect a person for months, years or even decades. Symptoms can be so severe that some sufferers may need to stay in bed and be treated in hospital during an episode.

It can be a frightening condition that affects everyday life, but the cycle is possible to manage with lifestyle changes and medication.

Read on to find out the answers to the following:

What are the symptoms?

Someone with CVS will go through a regular cycle of feeling ill, recovering, feeling well and then feeling ill again.

This cycle is made up of four phases:

1. Prodrome phase:

  • feeling that an episode is about to start
  • intense sweating and nausea for a few minutes to a few hours 

2. Vomiting phase:

  • retching and vomiting that often starts in the night or early morning
  • vomiting up to five or six times an hour for at least one hour, for up to 10 days
  • may not be able to move or respond 
  • other possible symptoms: abdominal pain, diarrhoea, fever, dizziness, headache, sensitivity to light, extremely pale skin, drowsiness or unresponsiveness, drooling or spitting excess saliva

3. Recovery phase:

  • vomiting and retching stop, and nausea subsides
  • recovery is gradual or immediate

4. Well phase:

  • a period of no symptoms  until the prodrome phase starts again

The cycle tends to be regular and predictable: the same symptoms, starting at the same time of the day, for the same duration each time.  

What is the likely cause?

The cause of CVS is currently unknown, but there may be a link with migraines. Many people with CVS develop migraines, and migraine medicines have been shown to help treat the syndrome. 

Vomiting episodes can sometimes be brought on by a trigger such as:

  • emotional stress, excitement, anxiety or panic attacks
  • an infection (such as a sinus infection or the flu)
  • certain foods such as chocolate, cheese, cured meats and foods containing MSG
  • caffeine
  • hot weather
  • menstrual periods
  • motion sickness
  • unhealthy eating habits  overeating, going without food for too long, or eating just before bedtime
  • physical exhaustion or too much exercise
  • sleep deprivation 

Who is affected?

CVS is most commonly seen in children  it's usually diagnosed at ages three to seven.

Children who suffer migraines and sensitivity to light and sound are more likely to develop the condition.

CVS can clear up by the time the child becomes an adult, although it can affect adults too.

It's not known exactly how common CVS is, but one study suggests that it affects around three out of 100,000 children.

How is a diagnosis made?

A GP will take their patient's family and medical history, and a full account of their symptoms.

A child may be suspected to have CVS if the following apply:

  • they have had at least five vomiting episodes, or three separate episodes over six months
  • the episodes of nausea and vomiting last from one hour to 10 days
  • the episodes are similar each time
  • they vomit at least four times an hour for at least one hour
  • the vomiting is not caused by another disorder
  • they are well between episodes

Similarly, an adult may have CVS if they have had three or more vomiting episodes in the past year that have each been similar, with no nausea or vomiting between episodes. 

The high frequency of vomiting, and the fact that it often starts at night or early morning, are clues that the cause may be CVS and not another condition.

Blood or urine tests may be carried out (to rule out infection or kidney problems), and scans such as an endoscopy or abdominal ultrasound, to see if there is an abnormality in the digestive tract.

Only after other conditions have been ruled out will a diagnosis of CVS be made. At this stage, the patient may have been referred to a gastroenterologist (specialist in digestive system disorders).

How should I manage a vomiting episode?

When a vomiting episode starts, it's a good idea to stay in bed in a dark, quiet room and take any medicines prescribed for this stage of the cycle.

Keep taking small sips of fluid to prevent dehydration – either water, diluted squash, diluted fruit juice or semi-skimmed milk.

Read about treating dehydration.

After the vomiting attack has finished:

  • drink plenty of fluids and gradually resume your normal diet
  • take any medicines prescribed to prevent future episodes

A child or adult who has been diagnosed with CVS will usually be under the care of a specialist, such as a gastroenterologist.


Drug treatment tends to be a process of trial and error. The patient may be given any of the following:

It may take a while to find a medicine or combination of medicines that work, as not all these treatments work for everyone.

Hospital treatment

If nausea and vomiting is severe, hospital admission may be necessary. Medicine and fluids may need to be given intravenously (directly into a vein) to relieve symptoms and prevent dehydration. Nutrition may also need to be given intravenously if vomiting continues for days.

Can vomiting attacks be prevented?

It may be possible to prevent or lessen vomiting attacks by:

Some medicines used to prevent migraines may also help.

What are the possible complications?

Severe vomiting episodes can lead to:

Further advice and support 

Cyclical Vomiting Syndrome Association UK

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