The blotchy appearance of skin color in the face and hands of older people is due to the uneven distribution of pigment cells and to changes in the interaction between melanocytes and keratinocytes. Sexual dimorphism
It has been observed that females are found to have lighter skin pigmentation than males in some studied populations. This may be a form of sexual dimorphism due to the requirement in women for high amounts of calcium during pregnancy and lactation. Breastfeeding newborns, whose skeletons are growing, require high amounts of calcium intake from the mothers milk (about 4 times more than during prenatal development), part of which comes from reserves in the mothers skeleton. Adequate vitamin D resources are needed to absorb calcium from the diet, and it has been shown that deficiencies of vitamin D and calcium increase the likelihood of various birth defects such as spina bifida and rickets. Natural selection may have led to females with lighter skin than males in some indigenous populations because women must get enough vitamin D and calcium to support the development of fetus and nursing infants and to maintain their own health. However, in some populations such as in Italy, Poland, Ireland, Spain and Portugal men are found to have fairer complexions, and this has been ascribed as a cause to increased melanoma risk in men. Similarly, studies done in the late 19th Century/early 20th Century in Europe also conflicted with the notion at least in regards to Northern Europeans.
Chills is a feeling of coldness occurring during a high fever, but sometimes is also a common symptom which occurs alone in specific people. It occurs during fever due to the release of cytokines and prostaglandins as part of the inflammatory response, which increases the set point for body temperature in the hypothalamus. The increased set point causes the body temperature to rise (pyrexia), but also makes the patient feel cold or chills until the new set point is reached. Shivering also occurs along with chills because the patients body produces heat during muscle contraction in a physiological attempt to increase body temperature to the new set point. When it does not accompany a high fever, it is normally a light chill. Sometimes a chill of medium power and short duration may occur during a scare, especially in scares of fear, commonly interpreted like or confused by trembling. Severe chills with violent shivering are called rigors. Causes
Chills are commonly caused by inflammatory diseases, such as influenza. It is also common in urinary tract infections. Malaria is one of the common reasons for chills and rigors. In malaria, the parasites enter the liver, grow there and then attack the red blood cells which causes rupture of these cells and release of a toxic substance hemozoin which causes chills recurring every 3 to 4 days. Sometimes they happen in specific people almost all the time, in a slight power, or it less commonly happens in a generally healthy person. See also
Cold chill
Goose bumps
Night sweats

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