The symptoms of Kawasaki disease usually develop in 3 phases over a 6-week period.

Phase 1: acute (weeks 1 to 2)

Your child's symptoms will appear suddenly and may be severe. Your child may be very irritable.

High temperature

The first and most common symptom of Kawasaki disease is usually a high temperature (fever) of 38C or above.

The fever can come on quickly and doesn't respond to antibiotics or medicines typically used to reduce a fever, such as ibuprofen or paracetamol.

Your child's fever will usually last for at least 5 days, but it can last for around 11 days without the proper treatment.

In some rare cases, the fever can last for as long as 3 to 4 weeks.

Your child's body temperature could possibly reach a high of 40C. 

Rash

Your child will almost always have a skin rash. This can vary in appearance from child to child.

Read more about skin rashes in children.

Hands and feet

The skin on your child's fingers or toes may become red or hard, and their hands and feet may swell up.

Your child may feel their hands and feet are tender and painful to touch or put weight on, so they may be reluctant to walk or crawl while these symptoms persist.

Conjunctival injection

Conjunctival injection is where the whites of the eyes become red and swollen. Both eyes are usually affected, but the condition isn't painful.

Unlike conjunctivitis, where the thin layer of cells that cover the white part of the eye (conjunctiva) becomes inflamed, fluid doesn't leak from the eyes in conjunctival injection.

Lips, mouth, throat and tongue

Your child's lips may be red, dry or cracked. They may also swell up and peel or bleed.

The inside of your child's mouth and throat may also be inflamed. 

Their tongue may be red, swollen and covered in small lumps, also known as "strawberry tongue".

Swollen lymph glands

If you gently feel your child's neck, you may be able to feel swollen lumps usually on one side. The lumps could be swollen lymph glands.

Read more about the complications of Kawasaki disease.

Phase 2: sub-acute (weeks 2 to 4)

During the sub-acute phase, your child's symptoms will become less severe, but may last a while.

The fever should subside, but your child may still be irritable and in considerable pain.

Symptoms during the second phase of Kawasaki disease may include:

• abdominal pain 
• vomiting
• diarrhoea 
• urine that contains pus
• feeling drowsy and lacking energy (lethargic) 
• headache 
• joint pain and swollen joints
• yellowing of the skin and the whites of the eyes (jaundice)
• peeling skin on the fingers and toes, and sometimes also on the palms of the hands or the soles of the feet

Phase 3: convalescent (weeks 4 to 6)

Your child will begin to recover during the third phase of Kawasaki disease, which is known as the convalescent phase.

Your child's symptoms should begin to improve and all signs of the illness should eventually disappear.

But your child may still have a lack of energy and become easily tired during this time.

The cause of Kawasaki disease isn't fully understood, but a child may be more likely to develop it if they inherit certain genes from their parents.

Infection

The symptoms of Kawasaki disease are similar to those of an infection, so bacteria or a virus may be responsible. But so far a bacterial or viral cause hasn't been identified.

As Kawasaki disease isn't contagious, it can't be passed from one person to another. This makes it unlikely that it's caused by a virus alone.

Kawasaki disease can affect children of any age. It can be more serious in children under the age of 1.

Genetics

The children who develop Kawasaki disease may be genetically predisposed to it.

This means the genes they inherit from their parents may make them more likely to get the condition.

One theory is that rather than there being a single gene responsible for Kawasaki disease, it may be the result of many genes that each slightly increase the chances of a child developing the condition.

Kawasaki disease is more common in children from northeast Asia, especially Japan and Korea.

This also suggests there may be a genetic cause.

There's no single test to diagnose Kawasaki disease, but there are some key signs that suggest a child may have this condition.

The National Institute for Health and Care Excellence (NICE) states that your child may have Kawasaki disease if they have:

• a high temperature (fever) of 38C or above for longer than 5 days
• at least 4 key symptoms

These symptoms include:

• conjunctival injection in both eyes – where the whites of your child's eyes are red and swollen 
• changes to the mouth or throat – such as dry, cracked lips or a red, swollen tongue
• changes to the hands and feet – such as swollen or painful hands or feet, or red or peeling skin on the palms of the hands or the soles of the feet
• a rash
• swollen lymph nodes in the neck

The skin on your child's fingers or toes may become red or hard, and their hands and feet may swell up.

Your child's hands and feet may also be tender and painful to touch or put weight on, so they may be reluctant to walk or crawl.

Read more about the symptoms of Kawasaki disease.

In some cases, Kawasaki disease may be diagnosed even if a child doesn't have 4 or more of the key symptoms listed above, or even if the fever has only lasted 4 days.

Tests

Your child may need to have tests to rule out other conditions that could be causing their symptoms.

Possible conditions your child could have include:

• scarlet fever – a bacterial infection that causes a distinctive pink-red rash
• toxic shock syndrome – a rare, life-threatening bacterial infection
• measles – a highly infectious viral illness that causes a fever and distinctive red-brown spots
• glandular fever – a viral infection that can cause a fever and swollen lymph glands
• Stevens-Johnson syndrome – a very severe allergic reaction to medication
• viral meningitis – an infection of the protective membranes that surround the brain and spinal cord (meninges)
• lupus – an autoimmune condition that can cause a range of symptoms, including fatigue, joint pain and a rash

Several tests can also be carried out to help support a diagnosis of Kawasaki disease.

These include:

• a urine sample – to see whether it contains white blood cells
• blood tests – such as a white blood cell count or platelet count
• a lumbar puncture – a sample of cerebrospinal fluid is taken by inserting a needle between the vertebrae of the lower spine

Individually, these tests may not be conclusive, but when combined with some of the key symptoms listed above, they can help confirm a diagnosis.

Heart problems

Complications of Kawasaki disease usually affect the heart. This means your child may need some tests to check their heart is functioning normally.

These must include:

• an electrocardiogram (ECG) – which measures the heart's electrical activity using flat metal discs (electrodes) attached to the arms, legs and chest; an ECG can identify damage to the heart or problems with the heart's rhythm
• an echocardiogram – this involves high-frequency sound waves used to produce images of the heart, which can confirm whether there are any problems with the heart's structure or function

During the acute phase of Kawasaki disease (weeks 1 to 2), several heart abnormalities may be identified.

These could include:

• a rapid heart rate (tachycardia)
• a collection of fluid in the heart (pericardial effusion)
• inflammation of the heart muscle (myocarditis)
• coronary artery swelling (aneurysms)

Read more about the complications of Kawasaki disease.

Kawasaki disease is treated in hospital as it can cause serious complications. Treatment should begin as soon as possible.

It may take longer for your child to recover if Kawasaki disease isn't treated promptly.

Their risk of developing complications will also be increased.

The 2 main treatments for Kawasaki disease are:

• aspirin
• intravenous immunoglobulin

Aspirin

Your child may be prescribed aspirin if they have Kawasaki disease.

This is one of the few occasions where aspirin may be recommended for a child under 16 years old.

Never give your child aspirin, unless it's prescribed by a healthcare professional. It can cause side effects, including Reye's syndrome.

Aspirin is a non-steroidal anti-inflammatory drug (NSAID).

It's used to treat Kawasaki disease because:

• it can ease pain and discomfort
• it can help reduce a high temperature (fever)
• at high doses, aspirin is an anti-inflammatory (it reduces swelling)
• at low doses, aspirin is an antiplatelet (it prevents blood clots forming)

The dose of aspirin your child is prescribed and how long they need to take it for depends on their symptoms. 

They'll probably be given high-dose aspirin until their fever subsides.

They may then be prescribed low-dose aspirin until 6 to 8 weeks after the start of their symptoms.

This is to reduce blood clots if there are problems developing in the blood vessels that supply blood to the heart.

Intravenous immunoglobulin

Intravenous immunoglobulin is also called IVIG. Immunoglobulin is a solution of antibodies taken from healthy donors. Intravenous means it's injected directly into a vein.

Antibodies are proteins the immune system produces to fight disease-carrying organisms.

Research has shown IVIG can reduce fever and the risk of heart problems.

The immunoglobulin used to treat Kawasaki disease is called gamma globulin.

After your child is given IVIG, their symptoms should improve within 36 hours.

If their fever doesn't improve after 36 hours, they may be given a second dose of IVIG.

Corticosteroids

Corticosteroids are a type of medication that contains hormones, which are powerful chemicals that have a wide range of effects on the body.

They may be recommended if IVIG hasn't been effective, or if your child is found to have a high risk of heart problems.

Read more about corticosteroids.

After treatment

When your child is discharged from hospital, you should be given advice about how to care for them at home.

This may include making sure they're as comfortable as possible and they drink plenty of fluids.

Make sure your child continues taking any medication that's been prescribed for them and look out for any side effects.

Your child will be given a follow-up appointment and their heart will continue to be monitored.

Once an ultrasound scan of the heart (echocardiogram) has confirmed that your child doesn't have any heart abnormalities, they can usually stop taking aspirin.

Full recovery could take around 6 weeks, but may take longer in some children.

Follow-up treatment may be needed if your child develops further complications.

Support

The Kawasaki Support Group and Societi, the UK Foundation for Kawasaki Disease can provide you with additional information and advice about your child's condition.

Aspirin side effects

Aspirin isn't usually given to children under the age of 16 because it can cause side effects, including Reye's syndrome.

Reye's syndrome is rare, but it can cause serious liver and brain damage, and be fatal if not treated quickly.

The symptoms of Reye's syndrome include persistent vomiting and a lack of energy.

Seek medical attention immediately if your child experiences either of these symptoms.

See the Yellow Card Scheme website for more information.

With prompt treatment, most children with Kawasaki disease make a full recovery. But sometimes complications can develop.

The complications associated with Kawasaki disease are mainly related to the heart.

They occur as a result of the inflammatory effect that the condition has on the blood vessels.

This sometimes affects blood vessels outside of the heart.

Aneurysm

Inflammation in the blood vessels that supply blood to the heart (coronary arteries) can cause a section of the artery wall to weaken.

As the blood passes through the weakened part of the artery wall, the blood pressure causes it to bulge outwards like a balloon. This is called an aneurysm.

This can cause either:

• a heart attack – where part of the heart muscle dies because it is starved of oxygen
• heart disease – where the heart's blood supply is blocked or interrupted

In rare cases, the aneurysm can burst (rupture), which could cause severe internal bleeding.

It's also possible for other major arteries to be affected, such as the brachial artery, the main blood vessel in the upper arm, or the femoral artery, the main blood vessel in the upper thigh.

Some aneurysms heal by themselves over time. But some children may experience further complications that require follow-up treatment with a specialist.

Risk of complications

Around 25% of children with Kawasaki disease who don't receive treatment – because the condition has been diagnosed incorrectly, for example – go on to experience heart-related complications.

The risk of developing complications is reduced for children who receive intravenous immunoglobulin (IVIG) to treat Kawasaki disease.

The heart-related complications associated with Kawasaki disease are serious, and may be fatal in 2 to 3% of cases that go untreated.

Children under the age of 1 are known to be at higher risk of serious complications.

Treating complications

If your child develops a serious heart abnormality, they may require medication or, in some cases, surgery.

Possible treatments include:

• anticoagulant medicines and antiplatelet medicines – medicines that stop the blood clotting, which may prevent your child having a heart attack if their arteries are particularly inflamed
• coronary artery bypass graft – surgery to divert blood around narrow or clogged arteries, and improve the blood flow and oxygen supply to the heart
• coronary angioplasty – a procedure to widen blocked or narrowed coronary arteries to improve the blood flow to the heart; in some cases, a short, hollow metal tube called a stent is inserted into the blocked artery to keep it open

Children with severe complications may have permanent damage to their heart muscles or valves, the flaps that control the flow of blood.

They'll have regular follow-up appointments with a heart specialist (cardiologist) so their condition can be closely monitored.

Complications in later life

If your child has had heart complications as a result of Kawasaki disease, they have an increased risk of developing cardiovascular complications later in life.

This includes conditions such as heart attacks and heart disease.

If your child has had complications from Kawasaki disease, it's essential that they have follow-up appointments with a specialist.

The cardiologist will be able to advise you about your child's likelihood of developing further heart-related problems.