Skin tone and radiance is determined by the amount of melanin pigment, oxyhaemoglobin (red skin pigment), as well as water and nutrients within the skin. Some of the reasons which causes dull and uneven skin tone are:

1. Internal factors– inherited factors, poor lifestyle, stress and tension, sleep deprivation, unhealthy diet, smoking & alcohol etc.
2. Environmental factors– dust, pollutants and poor air quality, exposure to extreme weather conditions, prolonged or excessive exposure to sun, some internal lighting and tanning sunbed may affects the skin’s condition. 
3. Skin factors–prolonged use of makeup and poor skin hygiene, lack of proper daily skincare, or incorrect skincare, can be a major factor affecting the skin’s condition.