The criteria are:
erythema of the lips or oral cavity or cracking of the lips
rash on the trunk
swelling or erythema of the hands or feet
red eyes (conjunctival injection)
swollen lymph node in the neck of at least 15 mmMany children, especially infants, eventually diagnosed with Kawasaki disease, do not exhibit all of the above criteria. In fact, many experts now recommend treating for Kawasaki disease even if only three days of fever have passed and at least three diagnostic criteria are present, especially if other tests reveal abnormalities consistent with Kawasaki disease. In addition, the diagnosis can be made purely by the detection of coronary artery aneurysms in the proper clinical setting. Investigations
A physical examination will demonstrate many of the features listed above. Blood tests

Complete blood count may reveal normocytic anemia and eventually thrombocytosis. Erythrocyte sedimentation rate will be elevated. C-reactive protein will be elevated. Liver function tests may show evidence of hepatic inflammation and low serum albumin levels.Other optional tests include:

Electrocardiogram may show evidence of ventricular dysfunction or, occasionally, arrhythmia due to myocarditis. Echocardiogram may show subtle coronary artery changes or, later, true aneurysms. Ultrasound or computerized tomography may show hydrops (enlargement) of the gallbladder. Urinalysis may show white blood cells and protein in the urine (pyuria and proteinuria) without evidence of bacterial growth. Lumbar puncture may show evidence of aseptic meningitis.
Because children with Kawasaki disease will be taking aspirin for up to several months, vaccination against varicella and influenza is required, as these infections are most likely to cause Reye syndrome.High-dose aspirin is associated with anemia and does not confer benefit to disease outcomes.About 15-20% of children following the initial IVIG infusion show persistent or recurrent fever and are classified as IVIG-resistant. While the use of TNF alpha blockers (TNF-α) may reduce treatment resistance and the infusion reaction after treatment initiation, further research is needed. Due to the potential involvement of the upregulated calcium-nuclear factor of activated T cells pathway in the development of the disease, a 2019 study found that the combination of ciclosporin and IVIG infusion can suppress coronary artery abnormalities. Further research is needed to determine which patients would respond best to this treatment.Corticosteroids have also been used,  especially when other treatments fail or symptoms recur, but in a randomized controlled trial, the addition of corticosteroid to immune globulin and aspirin did not improve outcome. Additionally, corticosteroid use in the setting of Kawasaki disease is associated with increased risk of coronary artery aneurysm, so its use is generally contraindicated in this setting. In cases of Kawasaki disease refractory to IVIG, cyclophosphamide and plasma exchange have been investigated as possible treatments, with variable outcomes.