Can cough syrup and vitamin C D drop cause napy rashes to my 4 month old baby?

Vit C Could. I think you are saying "diaper rashes" And yes the vitamin C could definitely cause a diaper rash due to its acidity. I would discontinue its use.

Related Questions

Can wheat plus 3 fruits crelac cause napy rash to my baby? . He also take vitamin C 5 drop daily. He is 4 month old

Not really. diaper (nappy) rash usually occurs if soiled diaper or nappy remains in touch with skin for long time. You may also want to change the type of diapers/nappy. Read more...