Cross-Reactions

Marmalade, Madeleine, & Mousse 2022

There are around ten significant cat allergens, and most people are allergic to more than one cat allergen, (just not as severe). The majority of cat allergies reactions to a small protein called Fel d1 (Cat #1). Quick side note: allergens are named by species and order of discovery, so Fel d1 = Feline domesticus 1 or (Cat allergen #1).

Severe allergies to horses, rabbits, dogs, or food allergies to pork, beef, or egg are always a concern in placing Siberian kittens, as many folks with these allergies react to even the lowest Siberians. Some individuals with severe cat allergies cross-react with other animals, but are unaware of the allergy because of lack of exposure.

We can safely place kittens in about 40% of these homes.  The remainder may be unable to safely have a furry pet. Because of this risk, we suggest starting with fur tests, and then spending time with a known low allergen Siberian.


Allergen Discussion:
Pretend a PaperMate Pencil and Papermate Pen are two different allergens in the same class. Your immune system can attach at different epitopes “latch-points”. Let’s say these places include the writing tip, barrel, shirt clip, and the eraser.  If your immune system latches onto the shirt clip of the Pencil, you will automatically react to the Pen.  If my immune system latches to the writing tip of the Pencil, I won’t react to the Pen. 

Looking at the three commonest cat allergens we why these “cross reactions” occur. 
Fel d 1 ~ Cat uteroglobin: does not share epitopes with most domestic animals.
Fel d 2 ~ Cat serum albumin: shares epitopes with Dog & Horse, Pork & Beef.
Fel d 4 ~ Cat lipocalin: shares epitopes with Horse, Boar, Mouse, Cow

Serum Albumin (Fel d2)
Serum albumin accounts for about 30% of cat cross reactions between cats, dogs, pork meat, or egg white, and reactions vary from mild to severe. Allergies from albumin can cause similar symptoms as allergies to Fel d1.

Albumin is a protein made by all animals. It holds fluids in the bloodstream and carries vitamins and enzymes through the body.  Cat albumin has all the same functions as albumin in other mammals, but the structure of albumin is slightly different in each species.

There are 6 different epitopes (latch points) on albumin. Our immune system can cross-react to albumins from different animals, as different species will have some identical epitopes and some that are slightly different. Our immune system is highly adaptable, so each person will reacts to allergens in a different manner.

Lipocalin (Fel d4)
Lipocalin is both a respiratory and dermal allergen, causing both asthma and skin reactions. About 25% of people with  horses/rabbits allergies react to feline lipocalin.  Studies show that intact male mice produce 500 to 1000 times more lipocalin than female mice, so neutering male cats might reduce lipocalin allergies

Horses are a significant sources of animal allergens. Up to half of folks with prolonged contact with horses develop reactions.  Anaphylaxis from exposure to horse albumin or lipocalin can occur in children without warning, though minor symptoms (asthma, itching, eczema) are usually present first. Carrying Childrens Chewable Benadryl  when allergic children visit horses can reduce the risk of dangerous allergic reactions.


.More detailed information about cat allergies: