Hi...I Am Extremely Allergic To Cats, And Was With Someone

Hi...I am extremely allergic to cats, and was with someone in my vehicle who owns a cat. Long story short, I rode with this person for 2 hours today, and have been sneezing and my nose running like crazy. I washed my clothes, took a shower, and Took 1 Allegra, and it has helped somewhat. Taken about 2 hours ago. Can I take another Allegra, or possibly a 1/2 one to help relieve my symptoms a bit more, or is this too much?

Thanks so much!