Dog in heat-- Aggresive?

Dogs do get aggressive when they're in heat. The cycle will last 21 days(3 weeks) & be sure to pick up some dog diapers & put them on her so there won't be blood anywhere. And I'm sure you already know this,but keep her away from male dogs. As for the allergy,contacts your vet & ask if there are any hypoallergic ways for a spaying procedure.