Allergies are many and varied, and symptoms can go from mild to severe. Most likely though, if you have this problem, you know that even slight allergies over a long time can be very draining.
Sometimes though, we’re put in situations that we can’t control where we’re exposed to something that we’re allergic to. Buying a house could be one of those situations. If the previous owners had pets, it is very likely that they left behind hair and dander that could affect you.
If there are carpets in the home, these can contain large amounts of allergens, and the same goes for filters and ductwork in the home. If you experience allergy symptoms in your new home, the first step should be to do a very thorough cleaning. For carpets, you should use a vacuum with a HEPA filter to keep the dander from becoming airborne and worsening the situation.
Getting a duct cleaning might cost a bit, but if just cleaning your home isn’t helping, that would be your next step.