Is it safe to take anti-allergy medicines while on birth control?

Antihistamines do not affect the efficacy of oestrogens and progestogens, which are the ingredients of the combined oral contraceptive.

It would be safe is you consult your doctor first on this because during this phase you need to be careful from all side which also includes cold, fever, allergy, etc drugs taken by your self.
The proper dosage and strength of medicine conformation is must before consumption.