The most common causes of blue freckles are early stages of a skin condition called blue nevi, which eventually develops into raised skin growths resembling moles with a noticeable blue tint. Although many people may be alarmed at the sight of blue freckles, this condition is usually non-cancerous. Just as with moles and other types of freckles, these skin spots result from a cluster of skin pigmentation cells called melanocytes that gather just under the surface of the skin's top layer. The blue color of these growths results from the melanocytes becoming packed tightly together and settling in the deeper layers of the dermis.
Most freckles result from excess sun exposure, particularly in fair-skinned individuals with a genetic predisposition to freckles. Orange or red freckles are especially prevalent in people with light skin, naturally red hair, and blue or green eyes. Other people can develop dark brown or even black freckles on areas of their bodies that are regularly exposed to the sun's rays, including the arms or shoulders. Blue freckles leading to nevi are different because medical researchers usually tie the blue color to specific mutations in the melanocytes that cause them to cluster with bits of collagen and form tiny nodules under the skin. These nodules appear as flat blue freckles in their early stages, but they later form raised and smooth grows on the skin's surface.
Dermatologists usually classify blue nevi as benign skin tumors that are normally more of a cosmetic than a real health problem. The most common areas of the body for these blue freckles are the torso, backside, and occasionally the hands or feet. People who dislike the appearance of these freckles can usually have them removed once their doctors have tested the spots to be sure they are not pre-cancerous growths.
A few rare cases of blue freckles indicate a type of cancerous skin melanoma, and dermatologists often classify this condition as cellular blue nevi. They normally need to perform biopsies on one of these skin growths to determine the presence of cancer cells. Freckles tied to this condition are generally larger than common blue nevi, and they tend to become raised from the skin surface at a faster rate. The freckle colors of cellular blue nevi can also be more varied, ranging from grey-blue to a deeper bluish-black. Treatments for this condition usually entail excision of the growth, and a malignant blue nevus usually has the best prognosis when caught early.