Kay wrote:
Afterbite and similar sticks contain some sort of ammonia compound, and
again relieve itching afterwards. I've found that they also seem to reduce
the swelling and blistering that I usually get from mozzie bites (I usually
get swelling as described by the OP, and a central area up to 1cm across of
yellow fluid-fillied blisters).

Definitely wasn't a mosquito - no itching, just a central dimple (presumably
where the bite started), a widening dark red patch, and a widening (but
shrinking again now, fortunately) raised swollen patch, which was very warm
to the touch when it was at it's peak.