MERV 11 does the trick during pollen season in Florida changing it every 3 weeks during Jan-March. Will try backing off to every 6 weeks when the worst is past. That appears to be the recommendation for highly allergic individuals, on a routine basis, throughout the year.
I'm very pleased. The filter fit perfectly and was shipped promptly. I read other reviews and I will say my experience was great. I will definitely order again They were a better price than my local supply store.