Common causes for spots on the skin include diseases such as low platelet count, meningococcal meningitis, shingles and tinea versicolor, according to Mayo Clinic, WebMD and the American Academy of Dermatology. In a low blood platelet count, the patient often bleeds internally, says Mayo Clinic. This is seen as spots on the patient's lower legs, called petechiae.
A rash is a danger sign in meningococcal meningitis, according to WebMD. The rash has a purple or red color and should turn pale when it is pressed. If it doesn't, it might indicate blood-poisoning, which is a medical emergency. Other symptoms of meningococcal meningitis are malaise, nausea or vomiting, pain in the joints, and a spiking fever. A severely painful headache that doesn't go away and a stiff neck are also symptoms.
Shingles occurs in people who have had chicken pox, says the American Academy of Dermatology. The virus that causes chicken pox is not destroyed after the disease runs its course, but lies dormant in the nerves. When the virus "wakes up," it causes symptoms that include a rash that turns into very painful blisters. The blisters are first clear, then crust over. The pain they cause diminishes after they heal, but residual pain can continue for years.
Early signs of tinea versicolor are spots all over the skin, says the American Academy of Dermatologyn. They can be many colors, are often scaly, dry and may itch.