It can be unsettling to notice an unusual or unpleasant smell emanating from blood. While blood naturally possesses a distinct odor, a perceived “stink” can raise concerns and often has underlying explanations.
Understanding Blood’s Natural Scent
Fresh blood typically carries a metallic or coppery scent. This distinctive smell arises from iron within hemoglobin, the protein in red blood cells responsible for oxygen transport. When blood is exposed to air, the iron reacts with oxygen, producing volatile compounds that our olfactory system perceives as metallic. This natural smell is usually subtle and not considered foul. However, a strong, unpleasant odor suggests a deviation from this normal perception.
Common Reasons for Perceived Foul Odor
An unpleasant odor from blood often results from its interaction with external factors or bacteria, particularly when exposed outside the body. Menstrual blood, for instance, is a combination of blood, uterine lining tissue, and an unfertilized egg, which exits through the vagina. When menstrual fluid mixes with the vagina’s natural bacteria and acidic environment, and is exposed to air, it can develop a distinct, sometimes musky, sweet, or metallic odor. This change in scent is frequently normal, but a strong fishy or rotten smell could indicate an imbalance.
Blood from a wound, especially if not promptly cleaned, can also develop a strong, unpleasant smell. This is primarily due to bacterial growth on the blood itself or within the wound tissue. When tissues die or bacteria metabolize substances in the wound, they can release malodorous chemicals. Dried blood also undergoes chemical changes that alter its smell. Additionally, blood mixing with sweat and skin bacteria can influence its perceived odor.
When Odor May Signal Other Health Concerns
Beyond external interactions, unusual body odors can sometimes point to deeper health issues. Infections, such as bacterial vaginosis, are a common cause of foul odors, often described as fishy, especially from vaginal discharge that may contain blood. These infections result from an overgrowth of certain bacteria, disrupting the natural balance. Similarly, severe wound infections can produce a putrid odor due to bacterial byproducts and tissue degradation.
Certain metabolic conditions, though rare, can also lead to unusual body odors that might be perceived as generally unpleasant. For example, trimethylaminuria (TMAU) is a genetic disorder where the body cannot properly metabolize trimethylamine, leading to a fishy smell in bodily fluids like sweat and urine. While not directly from blood, these systemic odors can be pervasive. Some medications and dietary factors can also subtly alter body secretions and their smells. Internal bleeding itself typically does not produce an external odor unless it mixes with other bodily fluids that then exit the body, such as very dark, foul-smelling stool in certain gastrointestinal bleeding scenarios.
When to Consult a Healthcare Professional
It is advisable to consult a healthcare professional if you notice a persistent or worsening foul odor from blood. This is particularly important if the odor is accompanied by other concerning symptoms. These symptoms may include fever, increased pain, unusual discharge (especially if it changes color or consistency), excessive bleeding, or signs of inflammation like swelling, redness, and warmth around a wound.
Changes in the color or consistency of the blood itself, or a general feeling of illness, weakness, or dizziness, also warrant medical attention. Any significant anxiety or concern about the odor should prompt a visit to a doctor. Self-diagnosis based solely on internet information is not a substitute for professional medical advice, and a healthcare provider can accurately assess the situation and recommend appropriate steps.