Cyclical vomiting syndrome: symptoms, triggers, treatment and what to do in an episode

The main symptoms are severe episodes of nausea and vomiting followed by periods of feeling well. The NHS says episodes begin with sweating, feeling sick and looking paler than usual, followed by retching and vomiting. Episodes usually start at the same time of day or night and last for the same length of time.

Other symptoms the NHS lists include exhaustion, loss of appetite, tummy pain, diarrhoea, dizziness, headaches and eye pain when looking at bright lights. The CVS Association adds that onset of vomiting is most commonly during the night or early morning, that vomiting may peak at up to 5 to 6 times per hour with violent retching, and that there may be extreme paleness, a low-grade fever, excessive salivation and lethargy.

• Severe nausea with repeated vomiting and retching.

• Sweating and looking paler than usual at the start.

• Exhaustion, loss of appetite and dizziness.

• Tummy pain, headaches and diarrhoea.

• Eye pain or discomfort in bright light.

• Feeling well between episodes, usually for weeks or months.

The NHS says avoiding triggers and taking medicines can help manage symptoms. Medicines may help if you have more than 1 episode a month. They depend on symptoms and age, and may include medicines used to treat and prevent migraines, anti-sickness medicines and painkillers. A doctor can also offer support if your child is struggling to cope with the symptoms.

If an episode is very severe, you may need to be treated in hospital with medicine and fluids given directly into a vein, to prevent dehydration and treat the symptoms. The CVS Association says treatment is otherwise supportive, that a dark, quiet environment is helpful during an episode, that treatment often progresses by trial and error, and that the same drug may help some people but not others, so there is no universal regime.

The charity urges caution about unproven "alternative" treatments, and points to guidelines for children and adults agreed by expert panels.

The NHS suggests staying in bed and sleeping in a dark, quiet room, and taking small sips of fluid such as water or diluted squash to prevent dehydration during and after vomiting. A pharmacist can recommend oral rehydration solutions that you mix with water and drink. Keep taking any medicine you have been prescribed.

Do not wait if you cannot keep fluids down. The NHS says to get help from NHS 111 now if you or your child keep being sick and cannot keep fluid down, or are peeing less than usual (or a baby has fewer wet nappies), and to call 111 for advice about a child under 5.

The NHS says an episode can last anything from a few hours up to a few days. The CVS Association says duration varies from a few hours to days between individuals, with the most common being between 12 hours and 2 days of vomiting (and 1 to 4 days overall), though it can range up to 10 days or more, and symptoms before the vomiting can spread over days.

Episodes are typically consistent for any given person. The charity says about 50% of sufferers show a strong regular pattern, with episodes as often as several times a month or as little as several times a year, and that it can persist for periods ranging from months to decades.

The exact cause is not known, but the NHS says you are more likely to have it if you or anyone in your family gets migraines. Episodes may be triggered by something, although the CVS Association says in many people nothing obvious starts an attack. Keeping a diary can help you spot triggers.

The NHS says a doctor will check whether your symptoms could be caused by cyclical vomiting syndrome and may ask how many episodes you have had and how long they last, how often you vomit during each episode, and whether you feel well between episodes and for how long. You may need tests to rule out other conditions.

The CVS Association says there are no diagnostic blood or urine tests for CVS, so it is usually a diagnosis by exclusion, and that getting a diagnosis may take several years with many tests and sometimes misdiagnoses. Formal criteria include recurrent, severe, discrete episodes of vomiting, intervals of normal health between episodes, episodes lasting hours to days, and no apparent cause.

The NHS says it often starts in children around 5 years old and improves as they get older, but can also affect adults, and is often more severe in adults who did not have the condition as a child. The CVS Association says it most commonly develops between the ages of 3 and 7, affects males and females equally, and that adult-onset CVS is more common than was once thought. Studies in school-age children in Australia and Scotland suggested that about 2% may be affected.

For children, call NHS 111 for advice if your child is under 5, and seek urgent help for dehydration signs such as peeing less or fewer wet nappies.

The NHS says to call 999 or go to A&E if you or your child have any of these signs, which could be signs of a more serious condition. Do not drive to A&E.

• Vomiting blood or vomit that looks like ground coffee.

• Green vomit in adults, or yellow-green or green vomit in children.

• A stiff neck and eye pain when looking at bright lights, or a sudden severe headache.

• A sudden, severe tummy ache.

• Blue, grey, pale or blotchy skin, lips or tongue.

• Severe difficulty breathing, or being confused or not responding as usual.

On the NHS, CVS is assessed by a GP, with referral to a gastroenterologist or paediatrician if needed, and treatment in hospital for severe episodes. The Cyclical Vomiting Syndrome Association UK and the Migraine Trust provide information and support, as the NHS notes. Private gastroenterology or neurology opinions are available, and results should be shared with your GP.