The reduction in quality of life and the personal economic effect from suffering allergy to cats is substantial as between 5% and 10% of the human population has at least some sort of sensitivity to cats. Interesting to note, allergies to cats are twice as common as dog allergies where cat allergens are among the most important indoor allergens and a common cause of IgE-mediated allergic disease world-wide.  Cat allergens are present in saliva, urine and sweat and are spread all over the cat's fur when it licks itself clean.  Tiny particles of dried skin (danders) that flake off the cat carry the allergen into the air where once breathed in by or get into the eyes of people allergic to cats will set off an allergic reaction.  As cats move around the house they leave danders on the surface of bedding and sofas that can be easily picked up by sensitized individuals to initiate an allergic reaction. Cat dander is pervasive as they can be airborne and survive for months or even years when trapped in carpets, rug mattresses, upholstered furniture and pillows.  Cat allergens are also detectable in many public places at levels capable of sensitizing or exacerbating symptoms in susceptible subjects making complete avoidance impossible.

The symptoms of cat allergy are initiated by histamine release in response to exposure to cat allergens and manifest as coughing, wheezing, chest tightening, itching, nasal congestion, rash, watering eyes, sneezing, hives, to potentially life-threatening asthma attacks. 

As with peanut allergy, allergies to cat is due to an oversensitive immune systems.  The immune system of cat allergic people mistake the harmless cat allergen carried on cat danders and fur as dangerous invaders and because they do not cause damage that is characteristic of bacteria and virus, the immune system sets off an allergic inflammatory response normally reserved for the killing of parasite invaders. 

Current treatment options for cat allergy are largely symptomatic where the first-line of defence are treatments with with nasal corticosteroids and antihistamines.  The only curative treatment in IgE-dependent allergic disease is allergen-specific immunotherapy (SIT). The allergen is given at increasing concentrations by different routes to affected patients over a period of time spanning many months. Allergen-specific immunotherapy (SIT) is the only disease-modifying treatment available today for desensitization to cats and has been demonstrated to be clinically effective in the treatment of both allergic rhinitis (sneezing and nasal congestion) and asthma. However, the treatment is both time consuming and resource demanding, and is associated with a high frequency of treatment-related reactions that can be severe and occasionally life-threatening thus limiting its broad use.

Sementis is developing a novel type of vaccine for the treatment of cat allergy that will not require the actual use of the allergen for desensitisation thus eliminating the risk of side effects as seen with the SIT approach but should eliminate both IgE-mediated and T cell–mediated allergic reactions shortly after vaccination resulting in a treatment course substantially shorter than with SIT.