Haemoglobin is a red-coloured pigment. If you have severe iron deficiency, there may be less haemoglobin in your blood and you may look pale. The is paleness easier on their face, nails, inner mouth and lining of the eyes. If you pull your lower eyelid down and it is a very pale peach colour or yellow, this may indicate that you have iron deficiency or iron deficiency anaemia.
Stoltzfus R, Edward-Raj A. Clinical pallor is useful to detect severe anemia in populations where anemia is prevalent and severe. J Nutr. 1999;129(May):1675-168