My son has just had his 4 year old immunisation needles & his right arm has swollen up & has a red rash. he says its itchy & is getting worse?

Shot reaction: It could be an allergic reaction, a poor shot administration into a vessel or it could also be an infection. You need to take him back to the doctor's office to have them look at it....Right now!

Give benadryl (diphenhydramine): see your pediatrician--it may be an allergy to a component but this is not life threatening--get it checked out but use benadryl (diphenhydramine) tonight.

Local Reaction: IT MOST LIKELY IS A LOCALISED REACTION.ALL YOU NEED TO DO IS PUT ICE ON IT AND IF ITCHING GIVE OVER THE COUNTER BENADRYL (diphenhydramine). IF SWELLING PERSISTS LET THE PEDIATRICIAN CHECK IT