Allergens in the home can bring on asthma or hay fever and even be the catalyst for various allergic reactions. Allergens are transported into your home via the air. They then land and settle all through your house, landing on surfaces such as counter tops and furniture. The airborne particles can be anything from pet fur and dander, mites, mold and insect droppings. Your HVAC system can help with this issue.
Here are some useful tips to reduce allergens in the house.

Look for signs of mold. If you have areas in your house that are humid and damp, mold could be thriving. Be sure to pay attention to your condensate drip pans, evaporator coils, the air handler and ducts throughout the house. Mold can be very dangerous to your health depending on its strain, so it is important to stay ahead of it.
Be sure to invest in furnace filters that are high quality. View them as your first attack on bad air quality in your house. A Merv 8 rating on a filter is what you should be looking for as they will do a good job of containing particles that are microscopic. It is important to check your filters once a month, but a good rule of thumb is to replace them around the 3 month mark. A dirty filter can’t do its job properly and will not be able to trap allergens. 
Preventative maintenance on your HVAC system is a great way to tackle allergens. Book an appointment at the start of spring to make sure your system is running to its full potential. This will keep it operating well and hopefully find small issues before they turn into big problems. Your technician will look to make sure there are no blockages and confirm your system is clean and helping you in the fight against allergens.
Dust, dust and dust some more! Dust over your vents and registers. By making sure the vents are clean dust won’t be circulated through the house. A damp cleaning cloth is a great tool to use so it traps dusts, and doesn’t just stir it up to go and land on another surface.
Check your units, both the outdoor and indoor units. Confirm they are free of blockage and debris. The air your unit pulls from the outside will circulate through your house. Removing dust and dirt from around the outside unit will help ensure your air quality inside your home is high.