A fever during 4 to 5 days is normal until the sixth day of the disease (without good reason), doctors should not prescribe antibiotics.
Hard-reduced fever is a sign of vasospasm. So, you need to add noshpa(Drotaverine is an antispasmodic drug) to an antipyretic. And, do not to inject cephalosporins.
If there is any suspicion, then you need to have an urgent blood test (detailed), where we consider the number of neutrophils (since ESR and white blood cells may increase due to various reasons). The level of lymphocytes increases with viral diseases. And with bacterial ones, the number of stab and segmented neutrophils increases sharply.
Children under 3 (or even up to 6 years old) almost should not have sinusitis, etc. They have neither maxillary sinuses nor frontal sinuses. Prolonged snot of any colour in 90% of cases means inflammation of the pharyngeal tonsil, which is adenoiditis, adenoids or reactive, secondary runny nose (if the child was “overmedicalized”).
With confirmed bacterial infections, the antibiotic is given strictly according to the course and nothing else. In the presence of vomiting the medicine is provided in the injections, in other cases – a liquid form.