hay fever and intense itching

I am taking zyrtec daily as dr ordered. It has been raining here for 3 days. Last night I opened door to let cat out and suddenly I began to itch like crazy. Benadryl didn't help so I got in shower. I slathered cortisone cream all over. I let cat back in and it happened again. what is going on? Went to town just now to get more zyrtec. The itching came back again. so back in the shower. I am spraying benadryl spray all over. Help!

I am allergic to hay, grass, most trees, horses, the mold on grass when it is wet. If it sunny and dry I can go outside and I am ok. just have to be careful going out on rainy humid days til everything has leafed out.