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Cyclical vomiting syndrome

Cyclical vomiting syndrome (CVS) is a rare disorder that usually starts in childhood. It causes repeated episodes of being sick (vomiting) and feeling sick (nausea).

The cause of CVS is not fully understood. The vomiting episodes are not caused by an infection or another illness.

CVS may improve as a child gets older, but it can also affect adults. The condition can be frightening, but it's possible to manage it with lifestyle changes and medicines.

Someone with CVS will feel very sick (nauseous) and may vomit for hours or even days at a time.

They'll recover from the episode and feel well, but they'll have another episode perhaps a month later, or sometimes longer.

CVS can last for months, years or sometimes decades. The symptoms can be so severe that some people need treatment in hospital.

An episode of CVS has 4 phases:

1. Prodrome phase

During the prodrome phase, the person will:

2. Vomiting phase


3. Recovery phase

During the recovery phase the:

Recovery can take a few hours to a few days.

4. Well phase

The well phase is a period where there are no CVS symptoms.

The cycle is usually regular and predictable, with the same symptoms starting at the same time of the day or night and lasting for the same length of time.

The cause of CVS is not yet known, but there may be a link with migraine. Many people with CVS develop migraines, and migraine medicines may help treat the syndrome. 

Vomiting episodes may be triggered by:

For some people, there is no obvious trigger.

CVS is more common in children, usually starting between the age of 3 to 7. But it can also affect adults.

Children who get migraines, are sensitive to light and sound, or have a family history of migraines, may have a higher chance of getting CVS.

Children with CVS may stop getting symptoms when they get older, but sometimes CVS continues. Having CVS as a child may also lead to experiencing migraines as an adult.

In children, a GP will ask about your child's symptoms and medical history. They may suspect your child has CVS if they show all these signs:

In adults, CVS may be diagnosed if:

The high frequency of vomiting and the fact the episodes tend to start at the same time of day indicates CVS, rather than another condition, may be the cause.

Blood or urine tests may be done to rule out an infection or kidney problems.

Tests, such as an endoscopy or abdominal ultrasound scan, may be done to see if there's a problem with your digestive tract.

Long-term use of cannabis can cause symptoms very similar to CVS (known as cannabinoid-induced hyperemesis).

You may be referred to a doctor who specialises in the digestive system (gastroenterologist).

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

Keep taking small sips of fluid, such as water or diluted squash, to prevent dehydration.

Signs of dehydration include peeing less than usual or having dark yellow and strong-smelling pee.

After the vomiting episode has finished:


You or your child may be prescribed medicine:

Read more about the medicines used to treat migraines and medicines used to prevent migraines.


Hospital treatment

You or your child may need treatment in hospital if nausea and vomiting is severe.

Medicine and fluids may need to be given into a vein (intravenously) to treat symptoms and prevent dehydration. Nutrition may also be given intravenously if vomiting continues for days.

It may be possible to prevent or reduce vomiting episodes by:

Some medicines used to prevent migraines may also help.

Severe vomiting and retching episodes can lead to:

The Cyclical Vomiting Syndrome Association UK and The Migraine Trust offer information and support for people with CVS and their families.