You should not have the seasonal flu vaccine if you have ever had an allergic reaction to a flu vaccine or one of its ingredients. This happens very rarely.
If you have had a confirmed very serious (anaphylactic) reaction to egg, have an egg allergy with uncontrolled asthma or another type of allergy to egg, your GP may decide that you should be vaccinated with an egg-free vaccine. One such vaccine is available for this flu season (called Preflucel, manufactured by Baxter Healthcare).
If no egg-free vaccine is available, your GP will identify a suitable vaccine with a low egg (ovalbumin) content, the details of which will be in the Green Book - Immunisation against infectious disease (PDF, 3.21Mb).
Depending on the severity of your egg allergy, your GP may decide to refer you to a specialist for vaccination in hospital.
If you are ill with a fever, do not have your flu jab until you have recovered.