The B-vitamin group consists of eight substances that all play important roles in cellular metabolism and other vital processes. B vitamins are water-soluble and excreted in the urine when in excess, making it necessary to replenish them regularly. Lack of certain B vitamins can precipitate mouth sores or cause skin irritation in and around the mouth. Mouth sores have many causes, but taking certain B vitamins can prevent or alleviate some types.
Mouth sores, or canker sores, are small painful ulcers inside the mouth. They usually have an inflamed, red border and may occur on the tongue, inside the cheeks or lips, and on the floor of the mouth. Canker sores are not contagious, which is in contrast to “cold sores” of the outer lips caused by the herpes-simplex virus. According to “Professional Guide to Diseases,” about 80 percent of mouth ulcers are small canker sores, whereas less than 10 percent are cold sores. Canker sores have multiple causes, such as trauma from chewing food or brushing teeth, weak immunity, excessive stress, hormonal changes and vitamin deficiencies. Most mouth sores usually take one to two weeks to heal, unless a vitamin deficiency is involved.
Vitamin B-12 Deficiency
Some people who experience recurrent canker sores have been found to be deficient in vitamin B-12, also called cobalamin. According to “Human Biochemistry and Disease,” normal blood levels of cobalamin range from 200 to 600 picograms per milliter for adults. Well-known symptoms of deficiency include pernicious anemia, which is characterized by immature red blood cells, and neurological issues similar to Alzheimer's disease, but recurrent canker sores occur as well. According to a study published in a 2009 edition of “The Journal of the American Board of Family Medicine,” researchers discovered that a nightly 1,000 microgram dose of vitamin B-12 is a simple, effective and low risk therapy to prevent recurrent canker sores. Vitamin B-12 deficiency is more common in men and women over 50, as the stomach begins to produce less acid and nutrients are not as easily absorbed, according to Harvard Medical School.
Vitamin B-2 Deficiency
Vitamin B-2, or riboflavin, is essential for normal growth, repair and development of body tissues, including the skin, connective tissue, mucous membranes and the immune and nervous systems. The recommended daily allowance for B-2 ranges from 0.3 milligrams for infants less than 6 months old, to 1.6 milligrams for lactating females, according to “Vitamins: Fundamental Aspects in Nutrition and Health.” Deficiency causes ariboflavinosis, which manifests as lesions of the skin, especially in the corners of the mouth, and a red, sore tongue. Lack of B-2 doesn’t lead to cankers, but it does result in mouth soreness from an inflamed tongue and cracks and fissures within the lips.
Vitamin B-7 Deficiency
Vitamin B-7, or biotin, is necessary for cellular growth, the production of fatty acids and the metabolism of amino acids. The recommended daily allowance for B-7 ranges from 5 micrograms in infants less than 6 months old to 35 micrograms for lactating females. According to “Nutrition and Diagnosis-Related Care,” deficiency is not common, but it can lead to symptoms in the hair, fingernails and skin, especially rashes near or around the mouth. These characteristic rashes are flaky but can become sore and inflamed over time.