Do antihistamines/anti-allergy medication affect the pill?

[Lauren Kirsty Meikle]

Hi, I am on the contraceptive pill, Yasmin, for almost 2 years now, and lately I have been developing worse and worse allergies, in particular to my boyfriend's house - he has a cat and the flat is very small. I spend most of my time there and need to do something to sort out my allergies, can I make a routine of taking antihistamines everyday, morning or evening, or would this interact with my pill?

And what about an allergy injection? Could I get this done or would it affect the pill?

Thanks in advance.