I (think) anti-histamene injections are now illegal in the UK because of heart complications - To be honest I've never really found an over the counter tablet that works without some sort of side effect, if I take any type of spray I end up with nosebleeds every day
BTW I think it's caused by an over active defence system, your body thinks it's under "attack", so goes through all the usual routines to prevent any foreign viruses entering... watering eyes, running nose, sneezing etc. I suppose that's why it's so difficult to prevent it, anything that works will be effectively "turning off" some of your body's very important defences.
Also, late evening in the summer is the worst time because during the day, the high air temp keeps the pollen quite high up and evenly distributed.. when the air cools down in the evening the pollen falls back down to ground level :thumbdown
If you're at home I suppose closing all windows etc before the evening gets cool would be a way of toning down the effects a little bit.