Re your cat... a friend of mine got new kittens, kept them upstairs. I went over recently and after 2-3 hours, I couldn't breathe. I had to leave.
Your cat has been in your home for 8 years. Yes, I think it's part of the problem.
We used to have a cat, many years ago, I never had a cat allergy. In the last 10 years, I have developed a cat allergy.
I would love to have another cat, my kids are DYING to have one, but now I know for sure I can't. It stinks.
I made the rounds at Cat Adoption events, asking for advice (before the recent experience at friends house) and one of the volunteers has a strong cat allergy, but she just takes OTC allergy medicine every day. So you can do that.
I hope the air duct cleaning will help. I can't hurt. Just make sure they do not damage your ducts. Ask them to verify how they will prevent damage.
Honestly, at this point, if you could find a home for your cat, you should. Your family should have sympathy for your condition as well. It's a horrible way for you to live.
Your husband should side with you (his wife) and not the cat (or the kids). I get that he loves the cat, but come on.
I'll tell you a story: 3 years ago I picked up an adorable, full grown, friendly, stray orange tabby. My kids loved the cat. I loved the cat. (My husband wasn't too happy that I just went ahead and brought home a cat.) I kept him in my daughter's bedroom because we have a big dog and I was terrified big dog would attack little cat. Within a week, I couldn't breathe anymore. Had to give cat away. At the time I didn't want to deal with living with shots or OTC meds to have a cat. I couldn't even think straight. All I knew was I had a big dog who didn't like cats, a husband who wasn't thrilled I brought home a stray without discussing it first and now, Allergies. I found a great owner who came to pick up cat. My kids were BAWLING in the street when the car drove away. I was not expecting that! But sorry! Cat had to go! I later found out cat was very happy in the new home, eating fancy take out leftovers every once in awhile.
In the 1990s, I bought an indoor air cleaner to help with the cat allergies. The problem (my dust allergies) were improved significantly. You might want to buy one of those babies. They are very pricey though. But if your husband really wants to keep the damn cat, then he has to shell out the money to help make you as comfortable as possible.
Do the kids help you dust/vacuum the house weekly?
Do you all that extra work by yourself?
Not fair. Every one has to chip in. Develop a plan.
If you can afford a cleaning person to come in, get that.
Your house needs a deep cleaning (probably that basement as well) and if you ever clean, you should probably be wearing a mask.
Can you pay someone to deep clean the basement for you?
If you are banned from a room in your own home - that's just not right.
Allergy Control Products is a very good company and good resource for information. I have dust mite allergies, so all my mattresses have a barrier and I wash all sheets 1x a week in HOT water. Comforters get washed 1x a month.
https://www.allergycontrol.com/t-catalogrequest.aspx