Suemarie,
In addition to the side effects (i.e. rash) that was mentioned above, there may also be more serious effects in 4% or so of the cases.
I was originally slated to be treated with Erbitux in addition to IMRT. Long story short, I was allergic to it and ended up in the ER due to an anaphylactic shock. This happened very quickly within 15 minutes of the first infusion. What was annoying in my case was that we told our MO that we thought that there was a chance of an adverse effect (I used to work with the type of mouse they used to make the MAB).

Note, if I could have tolerated it I would have gladly taken Erbitux. However, I also think that the patient needs to be watched very carefully during the infusion especially during the early phase and especially the first treatment. This is not always happening (certainly not in my case and not with my first MO...). It is a good idea to be watchful yourself.

Best
Markus