so you are having papular/vesicular type of rash on your body.starting up at your lower limbs
as you thought it definitely can also be because of the ALLERGIC REACTION
but what i want to know is if you have fever
as certain viral infection have these rashes as associated symptoms.
kindly show to your doctor for physical examination.as it is must for the diagnosis.
you can try cetrizine
to avoid it if its a allergic reaction.
hope it helps.