What is done to something to make it hypoallergenic?
It's not a word in any medical literature (just used for advertising purposes) ...except if someone is writing a critique on the subject.
The University of Toronto medical library and looking at two of best medical dictionaries there show no entry for hypoallergenic. The word does, however, appear in the Oxford English Dictionary. The venerable publication describes hypoallergenic as "a diminished potential for causing an allergic reaction."
Cosmetic companies first came out with "hypoallergenic" more on a basis so the consumer wouldn't actually ask if all the blurb on that particular product actually worked. The FDA did want the word removed, but the cosmetic companies said if this was the case then the price would go up on cosmetic products.
However, there are dog breeds (new breeds) coming out (gene pool) making a dog so-called hypoallergenic, but be wise, the magic word they use is "fur" and allergies don't come from the fur of the dog, but the dander from the skin.
Yorkies are supposed to be hypoallergenic but some people are still allergic to them. They are said to be hypoallergenic because they have hair not fur, but something about their saliva makes some allergic to them. The only way to know if you are allergic to them is by meeting one--since it depends on the person. :)