Why is my lower lip purple while the upper lip is normal? What should I do?
Mar 20, 2025
Source: Cainiu Health
Dr. Yang Ziqi
Introduction
Under normal circumstances, purple discoloration of the lower lip with a normally colored upper lip may be caused by cold exposure, excessive physical activity, local trauma, cheilitis (lip inflammation), or methemoglobinemia. It is recommended to seek medical attention promptly and follow the doctor's guidance for treatments such as general care and medication. In daily life, it is important to maintain a suitable environmental temperature and avoid exposure to substances that may cause poisoning.
Generally, purple lower lip with a normal upper lip may be caused by cold exposure, excessive exercise, local trauma, cheilitis, or methemoglobinemia. It is recommended to seek timely medical advice and receive treatments such as general care or medication under a doctor's guidance. Detailed explanations are as follows:
1. Cold Exposure
When the body is exposed to cold environments, peripheral blood vessels constrict to reduce heat loss, and this includes the blood vessels in the lips. Constriction of blood vessels in the lower lip decreases blood flow, reduces oxygenated hemoglobin, and increases deoxygenated hemoglobin, causing the lip to appear purple. It is important to stay warm in cold weather and wear a mask when outdoors.
2. Excessive Exercise
After intense physical activity, blood circulation accelerates to supply major muscles and organs, causing some degree of constriction in peripheral blood vessels, including those in the lips. This may lead to localized hypoxia in the lower lip, resulting in a purple appearance. Exercise should be performed in moderation, following a gradual progression, and proper warm-up and cool-down routines should be practiced.
3. Local Trauma
Injuries such as biting or bumping the lower lip can cause localized bruising and blood accumulation, resulting in a purple appearance. This may also be accompanied by swelling and pain. Patients may use medications such as Yunnan Baiyao ointment, swelling-relieving and pain-relieving tincture, or blood circulation-promoting pain-relief ointment as directed by a physician.
4. Cheilitis
Cheilitis is often caused by allergies, infections, sun exposure, or other factors. It damages the lip mucosa and disrupts local blood circulation, leading to inflammatory congestion and a purple appearance of the lower lip. Symptoms such as itching and pain may also occur. Treatments may include topical medications like tacrolimus ointment, pimecrolimus cream, or Kangfuxin solution, as advised by a doctor.
5. Methemoglobinemia
Methemoglobinemia may occur due to accidental ingestion of oxidizing agents like nitrites or due to congenital enzyme deficiencies. Hemoglobin in the body is oxidized into methemoglobin, which loses its ability to carry oxygen, causing the skin and mucous membranes—including the lower lip—to appear purple. Patients may also experience symptoms like difficulty breathing and dizziness. Treatment options include medications such as vitamin C tablets, coenzyme Q10 capsules, and sodium bicarbonate injection, as recommended by a physician.
In daily life, it is important to maintain a suitable living environment temperature, avoid exposure to potentially toxic substances, and reduce the risk of lip discoloration.
