Is it true that Cornish Rex cats don't evoke allergy?

It is partially true. If the allergy is evoked by the cat's hair, then a kitten of Cornish Rex breed is a good choice. Cornish rex cats are hairless, they have just an undercoat. But if the person is allergic to cat saliva enzymes or skin scales, thus, most likely you won't avoid allergy. As the cat grooms, it also spread allergens (which are in saliva) in its fur. So, allergens flit everywhere.
On purpose of purchasing a kitten and finding out the information about possible allergic reactions, it is best to visit the breeder at home and "communicate" with the pet, to squeeze the kitten, to palm it, to cuddle to your face and follow the reaction. If the allergy is displayed weakly, it is possible that after taking the kitten home, you won't feel it at all. It is just a one kitten and not the dozen that are grown by the breeders, thus, the reaction to the allergen of the organism should be easier. Most often in the course of time a person shakes down with this illness, there forms an immunity just like from vaccination.
Another variant - you can visit the allergist and consult for specific desensibilization. This is a treatment when particularly processed allergens are injected under the skin in small doses and organism is as if weaned onto tolerating the allergen. The treatment runs quite long and is not always successful.
Don't follow this clause blindly. Consult your doctor, visit the breeder and it will be easier to find the answer.
Good luck in looking for a right pet good to you and your family!