You can ring Healthdirect Australia (the 24hr Nurse on call thing) healthdirect Australia 1800 022 222 and they can help assess him over the phone. It might put your mind at ease even if you do end up taking him to hospital. Just to have immediate medical advice helps somewhat. Hmm... just looked at the website and it's not available in Queensland or Vic! Do you have an equivalent up there? I thought it was national! Will leave the number here anyway incase anyone else searches for it.

Just wondering - is fever common with an allergic reaction? It sounds more like an illness to me (my completely non-medical opinion!)

Hope he feels better soon