Hi, firstly I advice you to never give aspirin to kids as it may cause reye's syndrome. Secondly if you have recently gone out for a vacation or moved to a new place a recent change in drinking water can also be a cause, so kindly use only boiled water. Di tepid sponging with lukewarm water. Ask him about diarrhoea to rule out GI infections. Ask him about headaches, running nose, throat pain to ruleout upper respiratory tract infections. If he has ear pain, ear discharge etc it might be a ear infection.to treat infections you need antibiotics, so kindly consult a pediatrician for further management since the dose of medication varies between adult and kids, its never advisable to take medications on your own.