New House-Allergy Issues. Is a townhouse better?

I moved into a new house a couple years ago. Had major allergy issues. I tried everything from removing all carpeting, cleaning/sanitizing the ductwork, replacing the furnace, removing trees outside, scrubbing every inch of the house, etc. No luck, so I am relocating.

Here is my question: Do you think a townhouse would be better for allergies than a regular house, because most townhouses are newer construction (built more recently) than the old, 1950s houses that are being offered in my limited price range? Any thought on this? Are older houses loaded with allergens?

I lived in an apartment previously. The only change i can think of was the the apartment did not have forced air heating. It was a radiator, electric heat.

No changes. My lifestyle is very steady, consistent and predictable. It seems i developed these problems as soon as i moved into this house.

Before hopping to a really new building consider the materials. Some off-gas nasty, toxic stuff. Builders will use the cheapest stuff they can. I would be leery of townhouses for that reason.

I live in a 35-y-o house with carpets and a cat. My allergies are controlled by allergy shots and using the newer 4 inch filters in my furnace. My furnace has a special motor with 2 speeds, runs 24/7. It only takes power of 100 watt light bulb. As long as filters are changed 3-4 times a year I have little dust. I also have housekeepers once a month who dust, even up at top of walls with a long-handled floor mop. I use a rug scrubber once a year, but use only Bissell cleaning detergent. I've had reactions to cheaper products. My housekeepers use only vinegar for most cleaning, and a little Scrubbing Bubbles in bathrooms and rinse well. Chemicals used for cleaning are some of the worst things for allergies.

A couple of years ago I had to add grass to my allergy shots. Allergies can come and go, to some extent. The new rule for allergists is to test their patients every 3 years. Are you seeing an allergist? That would by my first step, before spending money on a new house.