Our baby had the BCG injection at birth four weeks ago. Now the site of his injection is red and raised - is this a normal reaction?

Yes this is normal. It is common following BCG vaccination for the site to become red and raised. It is also common to have an accumulation of pus, peeling or scaling or sores on the skin at the injection site. .It will heal up in time and I suggest that you see your Health Visitor or GP if you continue to be worried or if you feel that the skin is not healing or your child has a temperature and is unwell in any way.