People subjected to extreme cold can sometimes see their fingernails temporarily take on a bluish hue.(1) However, the condition usually clears up once they warm back up. In the case of chronic blue fingernails, causes include Raynaud’s disease, low levels of hemoglobin, and a variety of lung or breathing problems.
Raynaud’s disease affects the smaller arteries that supply blood to the skin.(2) The condition is more common among women than men, and also is a more frequent occurrence in areas with cold climates.
There are two strands of Raynaud’s. Primary comes without complications that can trigger “vasospasms,” while secondary—also known as Raynaud’s phenomenon—is more serious and generally affects people above the age of 40. The latter condition has many causal triggers such as lupus, rheumatoid arthritis, smoking, and bodily injuries.
Hemoglobin is a protein in red blood cells that transports oxygen.(3) Sometimes, when a person’s normal levels of this protein drop, they can encounter the symptom of blue fingernails.
Anemia is a leading cause of lower hemoglobin levels, and often requires the person suffering from this to start taking iron supplements as well as perhaps injected vitamin cocktail shots. Cancers such as leukemia, which destroy red blood cells, can cause the deficiency, as can malnutrition. At the other end of the scale, although very rare, people who drink too much water at a certain point and over-hydrate can also cause their hemoglobin levels to plummet. But this situation, as is the case with a large loss of blood, may cause at worse only temporarily bluish fingernails.
The scientific name for this bluish discoloration of fingernails and other parts of the body is cyanosis.(4) All sorts of lung issues can lead to this problem, including but not limited to a blood clot, infections, drowning, near-drowning, and severe pneumonia. Heart problems and even a drug overdose can also turn the fingernails blue.
Dr. Weil – “Why Are My Fingernails Blue?”, August 8, 2010, Retrieved October 16, 2011 from http://www.drweil.com/drw/u/QAA400771/Why-Are-My-Fingernails-Blue.html
Mayo Clinic – Raynaud’s Disease, Retrieved October 16, 2011 from http://www.mayoclinic.com/health/raynauds-disease/DS00433
National Institutes of Health – Hemoglobin, Retrieved October 16, 2011 from http://www.nlm.nih.gov/medlineplus/ency/article/003645.htm
National Institutes of Health – Skin Discoloration: Bluish, Retrieved October 16, 2011 from http://www.nlm.nih.gov/medlineplus/ency/article/003215.htm