Whether a cat has long, short hair or even no hair, it can still be the cause of an allergy. Allergic reactions are not triggered by the hair, but by the Fel d1 protein which is found in saliva, on the skin, in the urine and secretions of the sebaceous glands. When the cats licks himself, the allergen is transfered onto his coat and everywhere the hair goes: carpets, cushions, couches, bedding, etc.
The advantage with the Cornish Rex is that they shed very little hair, but that does not make it a hypoallergenic cat.
All cats excrete this protein to varying degrees. This explains why some people are more allergic to one cat than another.
According to some studies, the concentration of Fel d1 could be higher in non-castrated males. But no serious study proves that sterilized females, sterilized males, cats with lighter colored hairs or any other speculations are actually founded.
So you must be mindful before deciding to adopt a Cornish Rex if you suffer from allergies to cats. Do not adopt on a whim, let your emotions get the better of you or heed the faulty advice sometimes given.
To this date, few laboratories are screening for the amount of allergen in cats. Few studies are published and few resources are available for owners and breeders, so be careful before you believe in miracles.
Here are some references to learn a little more about allergies to cats.
Living with cat allergies – Hillspet
Treatment for cat allergies soon? – Maxisciences
Allergy to cat’s hair – LePointVeterinaire
Testing kittens for homes with cat allergies – Kittentesting
The Major Cat Allergen – Karger