Your first port of call is of course the allergy consultant but in my
opinion .....

I think the main thing to remember is that your current reaction ie
a bit of local swelling, is a different kind of reaction to
anaphylaxis or a systemic reaction.

Your local swelling is the sort of response that most people who are
stung by a wasp (and 2/5ths of the 50 microgram injection is
equivalent to about one full wasp sting because the typical wasp
sting is around 8 - 20 microgram) would get. In other words it is
perfectly normal and acceptable to have some local swelling when you
are stung and get a dose of venom. It is the body's natural
response.

A systemic reaction can occur to even the tiniest of doses of venom
and cascades through the body due to the body's own defense mechanism
and not because of the volume of venom. It is not a natural response
and it arises due to different sort of response pathways in the body.

There are two types of allergic reaction cells - T1 and T2 and a
normal allergic response is triggered by one type of cells and the
nasty anaphylaxis response by the other. As long as you are getting
a normal sort of reaction then I do think you should be absolutely
fine.

Wasp venom is a very nasty substance and the body is simply using its
defences to reduce the locally high concentration of venom. It is
not really indicative of anaphylaxis although it is understandable
that you might be anxious that it might be!

If you look back on this forum, most people have local swelling and
itching to their injections and get to the final dose.

Hope that helps a bit - but do have a word with the consultants as I
am sure they will be able to offer some reassurance too!

Best wishes

David