Birthmarks are pigmented spots on the skin that are present at the time of birth or occur shortly after birth. The pigmentation can occur in a number of different colors like tan, dark brown, purple, red, black, pink, white, pale and blue. It is not necessary for everyone to compulsorily have a birthmark. These colored spots can be flat or sometimes be raised slightly above the skin surface. In some cases, the pigments also extend to the tissues under the skin.
Acne is a skin condition resulting in the formation of red spots and pimples, especially on the face, neck, shoulders, back, chest and upper arms. Blackheads are a mild form of acne and are not painful to touch. These are usually caused due to the clogged hair follicles filled with oil and dirt. Acne appears as little red bumps whereas blackheads have a dark surface and may not be protruded like acne.