I am sorry to note that your 2-year-old niece is unwell with a chronic cough
that are not respnding to strong antibiotics.
I hope a Chest XRay has been done and has excluded a pneumonia. Sometimes pneumonia in little children can take longer to resolve leaving a chronic cough but if this prolonged, a cause must be established.
If infections with bacteria are common in her (such as sinusitis, pneumonia, skin etc) then a full blood count must be done and low lymphocyte count
excluded. If low lymphocyte count persists, antibody levels with CD3/4/8/19 levels must be done with IgG,A,M levels to exclude an immunodeficiency
(mostly antibody deficiency
). This is very rare but most important to exclude.
A chronic allergy such as to house dust mite, cockroach is more common and a chronic cough (mostly dry very occasionally wet) is seen. Reflux disease in children is also a cause of chronic cough at nights allong with asthma. A trial of omeprazole syrup and salbutamol
syrup/inhaler for 3-4 weeks can be recommended.
I hope this was useful.