L.S.
Give her the zyrtec. you can use OTC hydrocortisone cream or ointment. My best guess would be the chemicals or detergent left in the shirt. I would wash it. I wouldn't go see the pedi unless the bumps didn't go away. They could also be flea bites. I would hate for you to go and pay money for him to tell you he thinks they are bug bites and to take the zyrtec. and to use the OTC cream. I doubt it is the eggs as she has eaten them before. IF it were an allergy to the eggs, the bumps would not be only on her tummy and chest, they would be on her arms and legs and back, etc. which leads me to think it is the shirt or fleas or chiggers.
I wouldn't go to the doctor unless she had facial swelling, swelling of the lips, hives all over, or respiratory/breathing difficutlties, AND if all this stuff happens, then you should go directly to the ER. STAT!
But you said nothing happened. the spots may even be gone tomorrow.
I am not a take them quickly to the doctor kinda girl. I am an RN and I treat at home until either I don't know what else there is to do, need better medicine only a doctor can prescribe, or it is a true emergency. Then I only seek the ER for bleeding, lacerations, stitches, broken bones etc. But I am a nurse and pretty laid back. I have usually gone through all the common sense things I can think of before heading to the doctor, so he truly knows something is up when he sees us. And doesn't hesitate to educate me and treat the kids accordingly.
But you are the one that has to be comfortable. If it would make you feel better, than by all means take her and let the doctor take a look. I am only saying what I would do if I were in your shoes.
Good luck,
L.