Can a 6week old baby take antihistamines for a facial rash that appeared after putting some cream on?

No: Antihistamines are generally not recommended for infants. Please see your GP for an examination and treatment. In the meantime please keep moisturising the skin with simple fatty cream

See doctor: Theoretically antihistamines not licensed for under 2s but there are circumstances where they are useful. If the facial rash is some sort of dermatitis in general it won't respond that well to antihistamines (and if is a contact dermatitis may simply resolve with withdrawal of the cream) whereas if it is allergy it may but caution in this age group. Advise seeing a doctor for examination here.

No: The rash could be normal and if it is related to the cream remove it and see what happens unless the child is scratching it or has any other symptoms or concerns. When in doubt should see the doctor.