Some birthmarks are from extra color (pigment) in the skin. Other birthmarks are blood vessels that are bunched together or don't grow normally. It's not clear why some children have birthmarks and others don't.
a thickening of the cornea may indicate swelling swelling usually occurs from damage to the back the layer of the cornea associated with aging trauma or disease of the eye the swelling can be observed for progression or medically treated with topical hyper osmotic agents
Pathologically they are all the same-the skin has thickened in response to pressure. A callus generally refers to a more diffuse thickening of the skin (more common on the toes, but can occur under the ball of the foot) whereas a corn is a thicker more focal area area (more common on the toes).his thickening appears as a cone shaped mass pointing down into the skin. Hard corns are usually located on the outer surface of the little toe or on the upper surface of the other toes, but can occur between the toes. A soft corn occurs between the toes and are kept soft by the moisture in this area.