Blocking methods are generally used for various reasons such as to enhance the staining, prevent excessive background, or prevent false-positive staining. There are also a wide variety of methods that may be used to block endogenous biotin and serum for non-specific binding. There are other blocking methods such as enzyme and avidin-biotin blocking. A blocking method(s) of some kind is used in most IHC techniques and is almost always necessary. They usually bond to the charged sites of various tissue elements that are present in most tissues that result in non-specific staining.
