An internet search about dog breeds considered to be hypoallergenic will dish up a big old bowl of confusion. Many articles clearly state in their opening paragraphs that there is no such thing as a hypoallergenic dog breed. Then, they will go on to list hypoallergenic breeds. It's a real head-scratcher.
With a reported rate of 15-30% of the American public experiencing allergic reactions when exposed to dogs, the search for a companion that won't make a person have difficulty breathing is a valid one. Many experts agree that the claim that certain breeds are hypoallergenic is more about marketing than fact. "In a study measuring the level of allergen Can f 1 via enzyme-linked immunosorbent assay (ELISA) in breeds thought to be 'hypoallergenic' (Labradoodle, Poodle, Spanish Water Dog, and Airedale Terrier) found levels in the hair and coat of dogs as well as floor and airborne dust to be similar to non-hypoallergenic breeds."
The popular theory is that dogs that shed less are easier to live with for allergic humans. In reality, people are not actually allergic to falling hair but to the dander that dogs produce. The proteins that cause an allergic reaction in people are found in the dander (dead skin cells) and in the dogs' saliva and urine. All dogs breathe and pant and groom themselves, and all dogs produce urine, some of which ends up on their fur. Furthermore, older dogs have been shown to produce more dander and higher allergic reactions than younger dogs. This means that an allergic human might tolerate a healthy young puppy, but as the dog ages, the pet owner may find they have more allergy symptoms.
Some experts suggest that bi-weekly baths will help remove traces of saliva, urine, and dander from the pet, making breathing a little easier for those who share living space with them. Advertising allergen-reducing baths could be an excellent add-on service for groomers. Choosing a mild shampoo and following with a conditioner to keep the pet's skin healthy would be the way to approach this service.
The short answer to the question, "Are there any hypoallergenic breeds of dogs?" is no. Allergen levels vary widely, not only from breed to breed but also in specific individuals of any one breed. Even hairless dogs can produce allergens that make their owners miserable. Please don't buy into the myth created by people wanting to market the breed of their choice.
Resources
https://www.jacionline.org/article/S0091-6749(12)01380-2/fulltext
https://rivieraallergy.com/is-there-really-such-a-thing-as-hypoallergenic-dogs/
https://www.bay-porte.com/blog/hypoallergenic-dogs
https://www.nationwidechildrens.org/family-resources-education/700childrens/2020/11/myth-hypoallergenic-dog
https://finolagotto.com/blog/what-they-aren-t-telling-you-about-hypoallergenic-dogs