Thanks for your question on Health Care Magic.
I can understand your concern.
In my opinion, you should consult neonatologist for your child.
He is only 1.5 months old. In this age, immunity is low and possibility of lower
respiratory tract infection (LRTI) is more.
He might have contacted infection through family members.
So don't give medicines without consulting neonatologist in 1.5 month old child.
Get done clinical examination of respiratory system and chest
x ray if needed.
He may need antibiotics, antihistamines, inhaled treatment in appropriate doses according two his body weight.
Hope I have solved your query.
Wishing good health to your son. Thanks.