Fel d 1 is a protein that, in cats is encoded by the CH1 and CH2  genes. Fel d 1, produced largely in cat saliva and sebaceous glands, is the  primary allergen present on cats and kittens and what most people with cat allergies react to. 

Fel d 1 is also produced by cat skin itself.  

In 2010, Tom Lundberg along with UC Davis, developed a ELISA test to measure Fel d1. About half of the Siberians were found to have Fel d1 levels lower than other breeds, while under twenty percent would be considered very low. Individual Siberian cats from the naturally occurring breed native to the  Siberian region for which it is named, have been shown to have genetic variants that result in a lower production of Fel d 1. Contrary to popular belief, not all Siberians are low allergen. INDOOR Biotechnologies Laboratory, where our

 Fel d1 tests are done had this to say about allergen testing: 

A not-for-profit association of breeders, (Siberian Research Inc), was founded in 2005 to study allergen levels and genetic diseases in the Siberian breed. As of March 2010, fur and saliva samples from over 300 Siberians have been submitted for analysis, many directly from a veterinarian. Salivary Fel d1 allergen levels in Siberians ranged from  0.08-27 µg per ml of saliva, while fur levels ranged from 5-1300 µg. The high-end of these ranges is consistent with results from prior studies,  though the low end is below expected results. 

All Siberians tested were found to produce some Fel d1, with the  highest levels being found in Siberians that have silver colored fur.  Within the low group, males and females had comparable allergen levels.

Allergen testing for Fel d1 levels has come a long way in recent years. However it is very expensive and most Siberian breeders do not test their cats. 

Some breeders even believe the test to be inaccurate and that may have been true when the test was first developed. Now the test is accurate to 90% in adult cats and 80% in kittens. I encourage everyone who is thinking of adding a Siberian to their family to visit with a Siberian before they decide.  It's never easy taking a kitten home and having to return it because of allergies. I have to say that after many years of breeding and Fel d1 testing our cats, I still believe in science!

Because of allergen testing and through careful selection in our breeding of this magnificent cat, allergen levels in our Siberians have been significantly low. The proof? The families who come to visit our cats that have moderate to severe cat allergies and have no reaction! We have been very fortunate, we have never had a kitten returned. 

NOTE

Anyone with allergies to rabbits, horses, guinea pigs or eggs, will still react to a Siberian. They are reacting to a different protein, Fel d4.