Hello,
Since all of you are getting the hivesonly after moving into the new apartment, so the allergen has to be something in the apartment itself. It can be allergy to contactants, dust mites, pollen, mold or sopas or toiletries. Please give a thorough check on the new things over there and apply calamine lotion on the rashes. Also take Benadryl the next time, the hives appear. If the symptoms persist then please consult a dermatologist.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your dermatologist. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
Just a guess from a layman but maybe there's mold or asbestos in the walls.