My son has a small knot in his leg, it showed up after his 4 month vaccines. It has been 2 weeks since he had them (vaccines) and the knot is still there. Why is this and is it common? Should I take him to the doctor?
Baby Help Line:
Lump After Vaccination - Normal?
The lump that your son still has on his leg is quite a common side efect of the diphtheria-acellular pertussis-tetanus vaccine (DtaP).
It is due to a small inflammation caused by some of the injection material in the vaccine. It is not dangerous, nor painful and it can actually take even months to disappear.
The lump usually comes right after the shot, but it can also appear a few days later. As long as it doesn't hurt or change in size or color, there is no need to worry. It is called a DtaP granuloma, by the way.
If your son seems to be bothered by it, or if you worry that it isn't related to the shot, have his health-care provider look at it.