My 2 month old had bad congestion and my mom gave him onion juice. iam wondering is it safe?

Congestion: I would recommend nasal saline drops to be used and steam inhalation . Not sure about onion juice . Although will not harm .

Odd practice: The first months are troubled by narrow nasal passages & exposure to dust, fragrences, smoke & other irritants.Baby tries to flush these out of the nose with mucous but this often ends as congestion & produces 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.