The allergy caused in households and laboratories due to animal namely mouse is known as mouse epithelium. House rats are mainly of two types Rattus norvegicus or brown rat and Rattus Rattus or Black rat. They are most similar in their appearance and habits. Besides house rats, there are many species of wild rats too which too can cause animal allergen. Animal allergens majorly contribute to house and laboratory dust. The Rat dust which is a major allergic source contains allergens which are in Rate urine, epithelium and saliva. A lgE blood test is needed to detect the allergy caused due to these animal allergens.