Round Red Skin Patches / Rashes

Anyone na may ganitong case yung LO's niyo? I've been observing this rashes of my LO since nag 6 mos siya. Usually kapag lumalabas kami ng late afternoon pagbalik sa house may ganito na siya. Before na diagnose siya with Raseola after taking a certain vaccine but after that ganito na yung case. Just not sure if this is Pollen Allergy, Hives or sa Food (But usual naman lagi niya kinakain) Shes not taking any medications, nawawala naman after a week. Any advise or same case, anong ginagawa niyo and anong iaavoid?