If your're allergic to mold and mildew there's not much you can do. It will flare up when the rain causes the mold and mildew to become active. Dry any wet areas in (kitchen, bathroom) your apartment, use bleach (sparingly) to kill the suckers. If it's on/in walls there's not much you can do.
If it's an allergy to an outside allergan (grass, weeds, etc) consider vacuuming/mopping the apartment to get rid of any allergans brought in. Then when you're outside wear a jacket and a hat. If necessary (and if you won't get shot/arrested) wear a face mask. When you get inside take the jacket off and put it in a plastic bag. Do a quick wipe off of your face, hands, hair, pants and shoes with a damp cloth. Take a shower each time you go out and wash your hair. This keeps the allergans from getting on the furniture and sheets and pillows.
Not easy, but it works for us.
If the allergy meds aren't working could you try taking them more often than the recommended dosing? We do it without too much problems, but you would have to be alert for side effects.
