Blemishes are formed when oil, bacteria and dead skin cells become trapped in the pores on the skin. Normally, dead skin cells are brought to the surface of the skin by secretions from the oil glands and shed on a regular basis.
However, in skin that is prone to breakouts, excessive oil production casues these dead skin cells to bunch together causing a plug to form at the pore opening.
When a plug forms below the surface of the skin, which is commonly known as whitehead, bacteria naturally present within the hair follicle breaks down the accumulated material within the pore and turns it into irritating fatty acides. The enlarged pore and pressure within the hair follicle causes the fatty acids to leak through to the dermis below.
This infection not only casues blood celss to dilate, but also triggers the response of white blood ceels which causes redness and inflammation. This process results in the appearance of blemishes, which are red and tender and white capped imples, and in more server casese results in large cysts and boils.