Yes, there are lots of homeopathic remedies that you can take for hayfever, but you need to fit it to your symptoms first though.
If you get mainly watering and smarting eyes that are sore and itchy with profuse and acrid running of the nose then EUPHRASIA is a good remedy to take. This is commonly known as Eyebright and is effective if your hayfever mainly affects your eyes.
If you have predominantly nose symptoms, where your nose is streaming and there is acrid discharge and you have a dull headache with it and your eyes are smarting, sore and watery then ALLUM CEPA may help. This is the Onion and is helpful where you have predominantly nose symptoms that are burning and acrid and where your eyes are watering. Just think of what happens when you cut up an onion.
The two remedies that I have mentioned are the main remedies for hayfever but other remedies that may be helpful are ARSENICUM ALBUM. This can also be taken for a cold too. If your hayfever has no eye involvement, but you are constantly sneezing and streaming and you have acrid discharge where your lower lip and nose are red. If you feel chilly and are thirsty for small sips of cold water, then this remedy should be useful. If you feel hot or are very thirsty, then this is probably the wrong remedy.
APIS can be a good remedy to take for itching skin and when you come up in hives. It is made from bee venom and is good for wasp and bee stings and if taken quickly can also help in anaphylactic reactions also.
I hope this helps, but I would strongly urge you to get some RHUS TOX, which is poison ivy in potency, as I said before and if you take this your rash should resolve.
Also, I just have to correct you on one point. You do not have a disease at all. You have come into contract with poison ivy, which as its name suggests is poisonous, so it is your body's natural reaction to this to produce a rash. I know a rash can be itchy and unsightly, but it will resolve eventually and it is better than suppressing it and then getting more serious problems.