Use of ineffective cleanser or following a poor cleansing routine – results in accumulation of staled dead cells, hardened sebaceous secretion, salt (from sweat), waste, bacteria, dirt; as well as waxes, coloured pigments for those using makeup and/or fatty-based skin care products.Acne, is another one of the main cause of blackheads. It is caused by the overactivity of the sebaceous glands that secrete oily substances onto the skin. Other possible causes of blackheads are: * Genetics: If there is the history of blackheads in your family, then you are more prone to get affected by blackheads.* Hormones: The condition when hormones get imbalance, they may cause blackheads. Overactivity of testosterone in people prone to blackheads, triggers the sebaceous glands to produce an excess of sebum. At the same time, the dead skin cells lining the openings of the hair follicles are not shed properly and clog up the follicles.* Prescribed Medications: Some prescribed medications may also lead to formation of blackheads as a side effect , though this is a rare cause. * Oil Based Cosmetics : The oil based cosmetics may also induces blackheads due to allergic reactions.*

Blackheads – Causes, Symptoms and Treatment to Get Rid of it Soon Definition:Blackheads are small, dark spots which are the collections of oil and debris that clog pores. First of all, when it develops it’s called whiteheads – but as they come into contact with the atmospheric oxygen, a chemical reaction takes place and the mixture darkens and turns to blackheads. Unclean skin is a breading ground for blackheads. Blackheads are a mixture of dead cells of the skin, oil and bacteria.Blackheads are the primary lesions in acne. Blackheads, also known as open comdones, are flat, darkened spots. It is caused by a small plug of keratin and sebum within a hair follicle that is blackened at the surface in the opening of a follicle. Their dark appearance is caused by the densely packed skin cells, which take on a dark color. A term used to describe the skin’s pores clogged by natural oils and impurities. It is formed when oil and dead skin cells become trapped in a pore and mix with bacteria. They are called open comedones because blackheads are open to the skin’s surface and become darkened at the surface by exposure to oxygen (oxidation).Causes of blackheads:Some Important Causes of Blackheads includes:Blackheads are caused when sebum (the skin’s natural oil) collects and hardens in the pores. The toxins that are being expelled through your skin from the blood and lymph fluid combines with sebum creating a pasty glue. A blackhead occurs when the trapped sebum and bacteria partially open to the surface and turn black due to melanin, the skin’s pigment.

Source - oily skin clinical research NJ