Serosanguinous drainage refers to the clear, thin liquid that oozes from some wounds.

If you have an open wound, you may notice that the fluid draining from the site is often something other than bright red blood.

If the drainage is pale red, or if you see a clear liquid mixed with the blood, it’s probably serosanguinous drainage. This type of drainage typically isn’t cause for concern.

If the drainage is a different color, it may be a sign of infection. Knowing the difference between types can help you determine when to see your doctor.

Keep reading to learn more about serosanguinous drainage, as well as what the other types of wound drainage look like.

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Serosanguinous drainage is thin, like water. It usually has a light red or pink tinge, though it may look clear in some cases. Its appearance depends on how much clotted red blood is mixed with serum.

To better understand serosanguinous drainage, it helps to know the various components of blood.

Your blood has four basic parts:

  • Plasma: This is yellowish in color and contains serum, which is mostly water, and fibrinogens, which are proteins that help your blood to clot. Serum, which is clear, is plasma without the fibrinogens.
  • Red blood cells: These bright red cells help deliver oxygen from your lungs to the rest of your body. They’re the most commonly found cells in your blood.
  • White blood cells: These white cells help fight against infection.
  • Platelets: These are cell fragments that rush to an artery or vein that has been injured. Platelets clump together to form a clot. The clot helps cover the wound and slow or prevent blood from leaving the wound.

A wound draining fluid with both serum and red blood cells — serosanguinous drainage — could mean that capillaries have been damaged.

Capillaries are the smallest blood vessels in your body. Capillaries close to the surface of the skin can be easily injured when the dressing on a wound is changed. That means a scrape or wound with a larger surface area may be especially likely to produce serosanguinous drainage.

If the drainage is thin and clear, it’s serum, also known as serous fluid. This is typical when the wound is healing, but the inflammation around the injury is still high. A small amount of serous drainage is normal. Excessive serous fluid could be a sign of too much unhealthy bacteria on the surface of the wound.

Serum or blood-tinged serum are normal types of drainage from a healing wound. But there are other kinds of drainage that aren’t normal, and that may signal a serious complication.

The main types of abnormal drainage are:

  • sanguineous
  • hemorrhagic
  • purulent
  • seroprulent

If your wound is showing signs of abnormal drainage, see your doctor. They can determine why this is happening and treat any complications that have developed.

Deeper wounds involving thicker layers of tissue are more likely to produce sanguineous drainage, or thicker red blood. This typically occurs shortly after the wound has formed.

If red blood is still draining after several days, it may indicate that there has been further damage to the wound. This could be because you were too active after receiving the wound or because the wound wasn’t properly treated.

If sanguineous drainage continues to flow, it may actually be a sign of hemorrhage. Hemorrhage occurs if there’s been damage to an artery or vein.

If the blood is bright red and spurting, it may mean that an artery wall has ruptured. If the blood is dark red and steadily flowing, it may mean a vein has ruptured.

If the wound is small or shallow, applying direct pressure with a clean cloth or sterile bandage may be enough to stop the bleeding. After the bleeding has stopped, you should clean the wound, treated it with antibiotic cream, and cover it again.

If the wound is deep or large in surface area, you may need to see your doctor. If you’re unsure whether stitches or other serious attention is required, don’t hesitate to visit an emergency room or a walk-in clinic.

If the bleeding is uncontrolled, call your local emergency services.

Wound drainage that has a milky texture and is gray, yellow, or green is known as purulent drainage. It could be a sign of infection. The drainage is thicker because it contains microorganisms, decaying bacteria, and white blood cells that attacked the site of the infection. It may have a strong smell too.

If you see purulent drainage from a wound, see a doctor soon. Many infections won’t get better without treatment.

Sometimes serous drainage is also tinged with a milky, off-color fluid. If serum isn’t completely clear and pus is visible, it’s also a sign of possible infection.

Seropurulent drainage can also develop when an infection is clearing, but you should still have your doctor look it over to be sure.

It’s not just the appearance of wound drainage that is a concern. The amount of fluid emerging from a wound is important. Hemorrhagic drainage, for example, requires immediate attention.

One way to know if an artery or vein has been damaged is to note the way blood is flowing. A ruptured artery bleeds in spurts. A ruptured vein releases blood in a steady stream.

Purulent or seropurulent drainage may ooze slowly and a little at a time. Regardless of how much pus is visible or how it drains, it needs medical attention.

If you notice excessive sanguineous or serous drainage in the days after an injury or a surgical incision, see a doctor. Abnormal drainage may be a sign of an underlying complication. The only way to know for sure is to have your doctor examine your wound and investigate any other symptoms you have.

A fresh wound should drain more than one that is healing properly. If you’ve had surgery, a little serous or sanguineous drainage from the incision is normal. However, excessive bleeding could mean a blood vessel was injured during the operation. It could also mean that blood-thinning medications are preventing healthy blood clotting. You should tell your doctor if you notice drainage of any kind in the days after surgery.

Minor cuts and scrapes can usually be treated at home. If you have a wound treated professionally or undergo surgery, talk with your doctor about how to care for your wound and what to do if you notice any unusual drainage.

Serous and serosanguinous drainage are normal for the first two or three days. But you should watch for signs that the amount of blood mixed with serum is increasing. If this happens, see your doctor.

Paying close attention to a wound as it heals is vital. This may help you catch any complications early on and get the necessary treatment before further issues arise.