After a lifetime of various/numerous/DAILY inhalers, corticosteroids, meds, allergy shots, nebulisers, etc. etc...I had an UNBELIEVABLE response by simply taking an arthritis supplement with MSM (methosulfonylmethane); and within a few months my asthma virtually disappeared!!!
My experience:
Due to an outage, I tried a new formulation of Schiff Glucosamine with added MSM (1500 mg) for joint pain. After a few days noticed my asthma was easing (after decades of daily inhalers). After @ 3 months (time for inhaler refills) I noticed I had 2 unused inhalers unopened!
Then I stopped taking the Glucosamin/MSM for 3 months (during cancer surgery & recovery at family members house) and within 2 weeks my asthma returned and slowly began progressing. When I got home 3 moths later, I started the MSM again, and my asthma eased... more & more each day. Long story shortened: I did several trials (elimination tests, substitutions, etc) to make sure it was the MSM; and proved it was! After about 6 months using MSM, my asthma completely dissappeard! It's been over a year and I am completely asthma free (and I've reduced my dosage! Now take the MSM once every other day, or less; and I have no asthma; not even during pollen season!

During my research/trials I found many people have been helped/cured from asthma by using MSM (seemingly 'curing' thier sulfur deficiency)!
I also began using "sulfur soap" (bought for $1.00 at a Mexican Grocery store) on pimples, rashes, bug bites and other skin 'outbreaks', and it also proved miraculous for cleansing/healing!
I hope this helps you.someone!

For nasal/sinus problems; do a trial with MSM; and also try supplementing with Nattokinase and/or Sarrapaptase (both are systemic enzymes available at health food stores, health/vitamin shops); another cure for amny people.
For allergies in general ; try ingesting LOCAL raw honey from the locale where you are; the bees pre-process/digest the pollens for you, and perform as a desensitizer/immunotherapy (like allergy shots "desensitization" functions).