Ammonia, dabbed on straight after the bite, usually stops it flaring up. You can get ammonia roll-on sticks called After Bite, or just use the household stuff.

Personally if I lived in mosquito or midge country, I'd just avoid going out when the clouds of the little horrors are around - when the air is still and especially at dusk. They love me, but a bite on me swells up into a pus-filled, miserable, itching mound that bursts and risks infection.