There are many possible causes of red spots on the legs. Insect bites are a common cause, as well as allergic rashes and dermatitis. Depending on the underlying cause, various symptoms may accompany the appearance of red spots. If the spots are few and localized, they are probably not harmful, especially if they are not accompanied by other symptoms.
Red spots may be in the form of petechiae, which are small, pin-point spots that result from bleeding under the skin. Petechiae usually appear in clusters that look like a flat rash. These tiny spots are less than 3 millimeters in diameter and may indicate a wide range of conditions, including minor injuries to the blood vessels due to prolonged straining to serious medical conditions.
These medical conditions may include infections such as:
- Strep throat
- Scarlet fever
- Rocky Mountain spotted fever
- Viral hemorrhagic fevers
Non-infectious conditions that can lead to the appearance of petechiae include:
- Infantile scurvy
- Vitamin K deficiency
- Hemolytic uremic syndrome
Certain medications that can cause petechiae to appear in the skin include aspirin, atropine, carbamazepine, cimetidine, indomethacin, morphine, naproxen, nitrofurantoin, penicillin, and quinine.
Red spots that are caused by bleeding into the surface of the skin and are bigger than 3 mm in diameter are called purpura. They may be associated with a disease involving inflammation of small blood vessels such as Henoch-Schonlein purpura (HSP), but in some cases, the cause is uncertain, such as in idiopathic thrombocytopenic purpura. People who develop purpura usually develop symptoms such as a fever, fatigue, weakness, or a vague feeling of being ill. Purpura are often caused by a bleeding/clotting disorder and may be a sign of a serious infection that needs immediate medical treatment.
Red and purple spots and patches on the skin may be due to allergic or hypersensitivity vasculitis, which is an extreme immune reaction to a drug, foreign substance, or infection that leads to inflammation and blood vessel damage in the skin. However, in many cases, the exact cause is unknown. In this condition, hives, skin sores and blisters may also appear. Internal organs may also be involved, such as the joints, the kidneys and the gastrointestinal tract. The spots are often asymptomatic, but some patients report itching, burning, and pain. Treatment consists of anti-inflammatory medications, antihistamines, elevation of the legs and use of compression stockings.
Other possible causes of red spots or bruising under the skin include:
- Malnutrition, such as vitamins B12, C, K, or folic acid deficiency
- Chronic inflammatory disease, like lupus.
- Chronic liver disease, like cirrhosis.
- Certain types of cancer, like leukemia, Hodgkin's disease and multiple myeloma.
If you have unexplained red spots on your skin that do not improve with home treatments or are accompanied by other symptoms, consult your doctor to get proper evaluation and treatment.
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