It is present in the stratum corneum and fat cells of dermis and superficial fascia. Hemoglobin (also spelled haemoglobin): It is found in blood and is not a pigment of the skin but develops a purple colour. Oxyhemoglobin: It is also found in blood and is not a pigment of the skin. It develops a red colour.There is a correlation between the geographic distribution of UV radiation (UVR) and the distribution of indigenous skin pigmentation around the world. Areas that highlight higher amounts of UVR reflect darker-skinned populations, generally located nearer towards the equator. Areas that are far from the tropics and closer to the poles have lower concentration of UVR, which is reflected in lighter-skinned populations.In the same population it has been observed that adult human females are considerably lighter in skin pigmentation than males. Females need more calcium during pregnancy and lactation, and vitamin D which is synthesized from sunlight helps in absorbing calcium. For this reason it is thought that females may have evolved to have lighter skin in order to help their bodies absorb more calcium.The Fitzpatrick scale is a numerical classification schema for human skin colour developed in 1975 as a way to classify the typical response of different types of skin to ultraviolet (UV) light:

Ageing
As skin ages, it becomes thinner and more easily damaged. Intensifying this effect is the decreasing ability of skin to heal itself as a person ages. Among other things, skin ageing is noted by a decrease in volume and elasticity.
Gingivostomatitis is a combination of gingivitis and stomatitis, or an inflammation of the oral mucosa and gingiva. Herpetic gingivostomatitis is often the initial presentation during the first ("primary") herpes simplex infection. It is of greater severity than herpes labialis (cold sores) which is often the subsequent presentations. Primary herpetic gingivostomatitis is the most common viral infection of the mouth.Primary herpetic gingivostomatitis (PHGS) represents the clinically apparent pattern of primary herpes simplex virus (HSV) infection, since the vast majority of other primary infections are symptomless. PHGS is caused predominantly by HSV-1 and affects mainly children. Prodromal symptoms, such as fever, anorexia, irritability, malaise and headache, may occur in advance of disease. The disease presents as numerous pin-head vesicles, which rupture rapidly to form painful irregular ulcerations covered by yellow–grey membranes. Sub-mandibular lymphadenitis, halitosis and refusal to drink are usual concomitant findings. Signs and symptoms
The symptoms can be mild or severe and may include:

Not able to chew or swallow
Sores on the inside of the cheeks or gums
Fever
General discomfort, uneasiness, or ill feeling
Very sore mouth with no desire to eat
Halitosis (bad breath)

Causes
Herpetic gingivostomatitis is an infection caused by the herpes simplex virus (HSV). The HSV is a double-stranded DNA virus categorised into two types; HSV-1 and HSV-2. HSV-1 is predominantly responsible for oral, facial and ocular infections whereas HSV-2 is responsible for most genital and cutaneous lower herpetic lesions.