My Son Had Had 2 Reactions To Dtap Once When

My son had had 2 reactions to dtap once when he was 6 MIS and now his 18 month one has caused a HUGE painful lump it has been 3 mos it is getting bigger 1st ultrasound 6 weeks ago showed no fluid his pediatrician thinks he is sensitive to aluminum in shit I cannot find any info anywhere and I'm desperate for help in waiting to get spot with immunologist but it's really upsetting me