Every skin condition has its own symptoms. Some are determined by different type of spots either red or white, some causes inflammation and some give itchy bumps or irritation in skin.
Here are some details of the skin conditions which cause red spots on skin. These may be pigmentation problems in skin due to infection or some other reason.

Red Spots on Skin

Scleroderma:

Scleroderma is chronic skin affliction often causes red spots on skin. It is an autoimmune disorder. Size of red spots may very with time. First small spots appear and if no treated it become blushes. However scleroderma is non infectious and non cancerous skin disease. About 14 million population of earth have some form of scleroderma.
A form of protein called collagen it is responsible for increase in thickness and hardness of skin. Too much production of the collagen in skin consider as a causes of Scleroderma. Thought there are many theory regarding the causation of Scleroderma but actual causes are not fully known.

Symptoms of scleroderma vary from person to person, but hardness in skin over red spots is more general sign. Normally it is not so serious skin condition except some severe cases in which it would be life threatening skin problem.

Psoriasis:

Psoriasis red spots on skin covered by silvery white scaly patches. These patches of inflammation occur due to the rapid increase in the skin cell production cycle. About 8000000 million of USA population is suffering from this red inflammation condition.
Plaque psoriasis is the most common type of Psoriasis.

Eczema:

Eczema is an allergic skin condition that gives red spots on skin. Eczema is fairly chronic skin condition, normally it is difficult to get rid this skin condition where as it finished temporarily and reoccur after some time, and remain with a person all the life.

Mostly small children are victim of eczema. Some famous types of eczema are
1) Atopic eczema
2) Contact dermatitis
3) Xerotic eczema
4) Seborrhoeic dermatitis

Rashes:

Rashes use for the red, itchy bumps and itself it is not meant for any specific skin disorder.
Normally rashes are red spots on skin. These are bumps in skin change the appearance and feeling of skin. Some rashes occurs due to infection some are not and other are red itchy bumps on skin.