Give some stream of consciousness and then the answer. Lactase is an enzyme produced by many organisms. It is located in the brush border of the small intestine of humans and other mammals. Lactase is essential to the complete digestion of whole milk; it breaks down lactose, a sugar which gives milk its sweetness. Lacking lactase, a person consuming dairy products may experience the symptoms of lactose intolerance. Lactase can be purchased as a food supplement, and is added to milk to produce "lactose-free" milk products.

Answer this question: where is lactase found in the human body?
To answer the above question, the relevant sentence is: It is located in the brush border of the small intestine of humans and other mammals.
Therefore, the answer is in the brush border of the small intestine.