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Preschool children are the most vulnerable and are exposed to various illnesses ranging from malnutrition
, repeated infections, metabolic disorders and genetic disorders. So yes, it can be normal for child to be frequently ill if exposed to unhygienic conditions and found in areas of high endemic diseases. But most at times they are treated with readily available medications and if preventive measures are put into place, the child should normally not present with any infections (especially recurrent). If continuous illness or recurrent, then a pediatrician's attention is required immediately as child could be having an underlying diseases such as tumor
diseases, chronic infection etc
High temperature can can cause involuntary twitching reflexes including grinding.
My suggestion is to see pediatrician right now for proper assessment and treatment.