Allergic to one dog only - but not other dogs in same family?

[notthedogsfault]

Just pre-empting that the dog could be a red herring here, but I don’t have much else to go on.

We are good friends with a dog breeder, and have one of her puppies.

I’d never had any kind of allergic reaction - either to environmental factors or animals - until we stayed in the breeder’s home while she was away with her dog. Whenever I sat on the sofa (where her dog also sits), I had extremely itchy eyes and wrists and couldn’t stop sneezing - I ended up having to take an antihistamine any time I wanted to watch TV in the evening. This was quite a few years ago.

I forgot all about until now that we’re dog sitting the breeder’s dog - our dog’s mother - and I am having the same allergic reaction all over again.
I’ve never had even a hint of an allergic reaction to our dog, or to any other dogs. This includes another dog from the same litter/mother that we also dog sit occasionally, so I don’t think it’s a matter of having built resistance to our dog specifically…

I know it’s possible to be allergic to some dogs but not others. However, I assume it would be highly unusual for me to be allergic to the mother but not her children within that same family? Unless this is something that the mother can carry but not pass down to her pups?

Alternatively, it could be something that is in the breeder’s home and gets trapped in her dog’s fur?

Any ideas what might be going on here? It’s not a huge problem and I can manage it, but I’m curious.

Grateful for any pointers!

Dog shampoo. Flea treatment. I would look at products.

Having always had dogs and had no allergies at all, I now find that I’m really allergic to spaniels and some spaniel crossbreeds, although this seems to depend on how spaniely that particular dog is. I wonder if spaniels have something specific about their dander?

I also am fine with some labradors but not others, although this isn’t as pronounced as with spaniels.

It is possible to be allergic to only male dogs. There are several allergens produced by dogs most of which are in the hair, saliva and urine of all dogs. People can be sensitised to one or several of them.

However, one allergen (Can f 5) is specific to male dogs as it's produced in the prostate (with higher levels in unneutered male dogs). It is present in the saliva and urine of only male dogs and it is possible to be only sensitised to that allergen and be fine around female dogs and neutered males.