Fel d 1

The protein Fel d 1, produced largely by cat saliva and sebaceous glands, is the primary allergen present on cats. The protein is of an unknown function to the animal but causes an IgG or IgE reaction in sensitive humans (either as an allergic or asthmatic response). Removal of soft surfaces in the home (carpet, furniture), frequent washings of bed linens, HEPA filters and even washing cats have been proven to reduce the amounts of Fel d 1 present in the home. Fel d 1 is a particularly sticky protein and has been shown to cling to clothing and human hair and can be detected in environments where a cat has never been present.

Cats produce, on average, 2-7 µg of Fel d 1 per day. Studies have shown that intact males produce Fel d 1 in levels higher than castrated males, leading to the assumption that Fel d 1 is hormonally regulated by testosterone. Castrated males produce Fel d 1 in levels similar to females (both intact and altered females produce Fel d 1 in similar levels). Even though females and castrated males produce Fel d 1 in lower levels, they still produce enough to cause allergic symptoms in sensitive individuals.

Fel d 1 is an 18 kDa heterodimer protein and belongs to the secretoglobin family of small disulfide linked dimeric proteins found only in mammals.