I’m so sorry to hear about…

I’m so sorry to hear about your problems. I’m not a vet and can’t really give medical advice, but allergies certainly aren’t the only thing that could cause that problem. 

I’ve found some other resources:

https://canna-pet.com/swollen-paws-in-dogs-common-causes/

https://wagwalking.com/condition/inflammation-of-the-paws