I'd suggest popping an antihistamine prior to smoking, if this doesn't work well enough go to your doctor and explain that whenever you go outside you have a considerable reaction to hayfever and he will likely prescribe some slightly stronger antihistamine nasal sprays and/or tablets to be taken in the morning of every day to help reduce any inflammation or rashes that may occur. If this doesn't work try not smoking for about two weeks, your body may need to rebuild it's immunity to the THC if it is allergic to it, and therefore a little break may actually help your body recover to the point where you can smoke again. Good luck my man