Answer:
In neonates, (and infants under, I think, 6 mo) the child lacks the shiver reflex, nor are the rest of their temperature regulating responses as developed.
In the elderly, the skin tends to thin with age, the blood supply to the epidermis lessens as does is the amount of subcutaneous fat tissue and the number of sweat glands. These skin changes cause the efficiency of the body's temperature regulation systems, AND can cause an elderly person not to be as aware of the surrounding temperature increasing the likelihood of temperature related conditions like dehydration, heat stroke, hypothermia and frostbite.
