However, the best thing that you can do is to keep using flea prevention products. In the meantime to help you Pom with this allergic reaction:
1) Use a gentle, quality canine shampoo & condition and bathe your Pom gently as to not rub the skin but do allow the products to do their work to moisturize.
2) Be sure to treat the home, as well, so that new fleas cannot jump onto your Pom. If your Pom has had fleas, you can be 100% certain that there are fleas on your carpeting, sofa, beds and more...even if you cannot see them and even if their tiny bites do not bother human household members.
3) Keep an eye on areas that your Pom may have scratched heavily to make sure that infection does not set in.
4) Talk to you vet about giving your Pom antihistamines while he is fighting this allergy.
5) In severe cases, oral steroids may be given to help a dog with the extreme suffering
A Random Flea Bite or an Infestation
There is a huge difference between using a product to repel fleas and using that same product to try and deal with an infestation. Once must remember that prevention does just that, it works to prevent fleas from embedding themselves into the coat of a dog, essentially setting up shop there.
Sometimes prevention does not work...and this can happen for a variety of reasons - It may have been near the end of the course and a puppy came into close contact with another puppy that had fleas, a dog may have come into close contact with fleas and the product just was not strong enough, a certain product may work very well on one dog but not work well on another, etc.
In a case like this, if fleas have broken past the protective barrier and are in the coat, eating and biting making a home for themselves, it is time to treat this as an infestation. And at this point, a barrier type product simply will not do. Not only will the tiny little creatures be setting up house on the dog's body, they will also jump to the carpeting, sofas, beds, etc.
The house will need to be fumigated and the dog should be (under the supervision and "okay" of a veterinarian, dipped in flea bath formulas to kill the existing critters and also any eggs. If a Pomeranian visibly has fleas, you can bet for sure that eggs exist as well.
Once all has been treated and the fleas are gone, it will then be time to re-think prevention, either better staying on track in regard to regular dosing or by switching to a more effective brand.