I have a 3 months baby. he is caughing what's the best medication ?

None: The first months are troubled by narrow nasal passages & exposure to dust, fragrances, smoke & other irritants.Baby tries to flush these out of the nose with mucous but this often ends as congestion & produces cough & rattling with breathing. The best rx is washing out the nose with saline & suctioning the remainder. Eliminate irritants from babies environment & this will happen less.