If it's seasonal allergies, I recommend taking something like Claritin (a) to relieve your symptoms and (b) to rule out the possibility that it's something else. I have allergies, too, and I don't generally feel achy, so I have to wonder if you have something else.
I'm arguably a wimp, but I tend to lay off exercise when I'm sick. My immunity is already down and taxing my body further isn't likely to help. I've also read that exercising with a viral infection can actually harm your heart muscle. Since it's so hard to tell if an infection is viral or bacterial, I generally just don't take any chances. I'd rather just take the time off and come back strong. In fact, some of my strongest rides have been after a week of being laid up. It proves the point, in my mind, that rest is sometimes not only the best thing for your body, but also for your performance.
Listen to your body. If you think you need rest, then go ahead and rest. If you think getting up and moving around will help, then do so, but take it really easy.
I hope you feel better soon.
Live with intention. Walk to the edge. Listen hard. Practice wellness. Play with abandon. Laugh. Choose with no regret. Continue to learn. Appreciate your friends. Do what you love. Live as if this is all there is.
--Mary Anne Radmacher