What causes welts that turn to bruises?

1. Pressure urticaria (pressure hives): These welts are caused by applying pressure to the skin, such as from a tight waistband or a heavy object. They typically develop within minutes and can last for several hours.

2. Dermatographism (skin writing): With this condition, stroking or scratching the skin causes a raised, red line to form. This line can then develop into a welt or a bruise. Dermatographism is thought to be caused by an overactive response of the body's immune system to minor injuries.

3. Allergic reactions: Certain allergies, such as those to insect bites or stings, foods, or medications, can cause welts that turn into bruises. These welts are typically accompanied by other symptoms, such as itching, swelling, and difficulty breathing.

4. Vasculitis: Vasculitis is a condition that causes inflammation of the blood vessels. It can lead to a variety of symptoms, including welts, bruises, fatigue, and joint pain.

5. Blood clotting disorders: Certain blood clotting disorders, such as hemophilia and von Willebrand disease, can cause easy bruising and bleeding. This can lead to the development of welts that turn into bruises.

6. Vitamin deficiencies: Deficiencies in certain vitamins, such as vitamin C and vitamin K, can cause easy bruising.

7. Infections: Some infections, such as mononucleosis and Rocky Mountain spotted fever, can cause welts that turn into bruises.

8. Medications: Certain medications, such as aspirin and anticoagulants, can increase the risk of bruising.

9. Pregnancy: Some women develop welts that turn into bruises during pregnancy. These are thought to be caused by changes in hormone levels.