my girl & my sister's son also have the same skin problem when they got the injection at 1 yr old. You must see doctor to get medicine to control it. If it's too much, it may spread to her inner body like lungs,etc & that will be very dangerous.
Of course, be relaxed. If medicine is taken, it will be ok in a few days.
for those baby not yet injected this 1 yr old vaccination, you may consult doctor as many private baby clinics offer the "low allergy" one but of course with a cost (around $400) compared to free one in government's clinic. But if you kid is allergy to eggs or milk, you better pay the extra cost as you may have a great chance of bringing your baby to see doctor afterwards as such allergy will cause fever & spots in skin which must need medication to cure.