Cyclical vomiting syndrome (CVS) is a rare disorder that mainly affects children. It causes repeated episodes of vomiting and feeling sick.

CVS has no apparent cause – the vomiting episodes aren't the result of an infection or illness.

It can be frightening, but it's possible to manage CVS with lifestyle changes and medication. It usually clears up before adulthood.

Symptoms of CVS

Someone with CVS will feel very sick and may vomit for hours or even days at a time. They'll recover from the episode and feel perfectly well before having another episode perhaps a month or so later.

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

An episode of CVS has four distinct phases:

1. Prodrome phase

During the prodrome phase, the person will:

• feel an episode of vomiting is about to start
• have intense sweating and nausea for a few minutes to a few hours
• appear unusually pale

2. Vomiting phase

The vomiting phase involves nausea, vomiting and retching. The person may:

• have periods of retching and vomiting, which can last for 20 to 30 minutes
• vomit up to 5 or 6 times an hour, for up to 10 days
• be unresponsive and unable to move
• have other symptoms, including abdominal pain, diarrhoea, fever, dizziness, headache, sensitivity to light, very pale skin, drowsiness, drooling or spitting excess saliva

3. Recovery phase

During the recovery phase:

• vomiting and retching stop, and nausea subsides
• other symptoms improve

Recovery can be immediate or gradual.

4. Well phase

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

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

What causes CVS?

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

Vomiting episodes can sometimes be triggered by:

• emotional stress – excitement, anxiety or panic attacks
• an infection – such as a sinus infection, respiratory infection or the flu
• certain foods – such as chocolate, cheese, cured meats, and food containing MSG (monosodium glutamate)
• caffeine
• hot weather
• periods
• motion sickness
• unhealthy eating habits – overeating, not eating for long periods or eating just before bedtime
• physical exhaustion or too much exercise
• sleep deprivation

Who's affected

CVS tends to occur in childhood, with around half of those affected having symptoms before the age of three.

CVS often clears up by adulthood but can sometimes continue into it.

Children who get migraines and are sensitive to light and sound are more likely to develop CVS. Having a family history of migraines also increases your risk.

Diagnosing CVS

For children, your GP will ask about your child's symptoms and medical history. CVS may be suspected if all of the following criteria are present:

• at least two or more intense and continuous episodes of nausea and vomiting lasting from hours to days within a six-month period
• episodes are similar each time
• episodes are separated by weeks to months, with a return to normal health between episodes
• following medical assessment, the symptoms can't be attributed to another disorder that causes the vomiting

In adults, CVS may be diagnosed if you've had three or more similar vomiting episodes in the past 12 months, with no nausea or vomiting between episodes, and another condition isn't the cause.

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

Blood or urine tests may be used to rule out an infection or kidney problems. Scans, such as an endoscopy or abdominal ultrasound, may be carried out to see whether there's an abnormality in the digestive tract.

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

CVS will only be diagnosed after other conditions or potential causes have been ruled out. By this stage, you may have been referred to a gastroenterologist, a specialist in digestive system disorders.

Managing a vomiting episode

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

Keep taking small sips of fluid to prevent dehydration. Water, diluted squash, diluted fruit juice or semi-skimmed milk are best.

After the vomiting episode 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's been diagnosed with CVS will usually be under the care of a specialist, such as a gastroenterologist.

Medication

A number of medicines can be prescribed to help treat and prevent CVS. For example, you or your child may be prescribed:

• medicine to prevent nausea and vomiting
• medicine for abdominal pain – such as ibuprofen or amitriptyline (for those older than five years)
• medicine to control stomach acid production – such as ranitidine, lansoprazole or omeprazole
• migraine treatments – such as sumatriptan and propranolol; read more about the medicines used to treat migraines and medicines used to prevent migraines

It may take a while to find a medicine, or combination of medicines, that works for you.

Hospital treatment

Hospital treatment may be needed if nausea and vomiting is severe. 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.

Preventing vomiting

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

• avoiding known triggers, such as certain foods
• getting enough sleep
• treating any sinus problems or allergies
• taking steps to manage stress or anxiety
• eating small carbohydrate-based snacks between meals, before exercise and at bedtime – this can help prevent future attacks in some people

Some medicines used to prevent migraines may also help.

Complications of CVS

Severe vomiting and retching episodes can lead to:

• dehydration
• inflammation of the gullet lining (oesophagitis)
• a tear in the lining of the gullet
• tooth decay
• gastroparesis, where the stomach is unable to empty itself of food in the normal way

Help and support

The Cyclical Vomiting Syndrome Association UK can provide further information and support for people with CVS and their families.