Vitamin B2 (abbreviated as B2), also known as riboflavin, is easily destroyed by heat and light in alkaline solutions. In the body, B2 is converted into FMN (flavin mononucleotide) and FAD (flavin adenine dinucleotide), which then participate in the composition of the prosthetic group of flavoenzymes. Flavoenzymes are key components of the biological oxidation system—the respiratory chain. Therefore, B2 is widely involved in various biological oxidation-reduction reactions in the body, promoting the metabolism of carbohydrates, fats, and proteins, making it essential for growth and tissue respiration. B2 is widely distributed in nature, but animal-based foods contain higher levels than plant-based foods. Those who primarily consume plant-based foods tend to have lower B2 intake. The recommended daily dietary allowance for B2 is 0.4 mg for infants and 0.6–1.8 mg for children and adolescents.

bubble_chart Diagnosis

(1) History: A history of insufficient dietary intake of B2; a history of diseases causing malabsorption of B2, such as chronic gastrointestinal diseases, liver diseases, and reduced B2 absorption due to treatment with probenecid or phenothiazines; a history of increased B2 requirements, such as rapid growth periods, acute or chronic infections, trauma, and phototherapy for neonatal hyperbilirubinemia.

(2) Clinical Manifestations

1. Lip and tongue symptoms: such as angular stomatitis, moist, erosive, fissured, or ulcerated corners of the mouth; cheilitis, with bright scarlet-red lips and vertical fissures; glossitis, with a smooth, bright red tongue, reduced or absent papillae, and fissures on the tongue surface.
2. Ocular symptoms: such as vascularized conjunctivitis, keratitis, or iritis, leading to photophobia, tearing, itching, or burning sensations.
3. Skin symptoms: mainly seborrheic dermatitis, often occurring at the nasolabial folds, nasal wings, behind the ears, or eyebrows, initially with excessive sebum secretion, followed by crusting. Additionally, scrotal dermatitis may also be present.

bubble_chart Treatment Measures

(1) B2 treatment: The oral dose for children is 1mg (or 5mg) each time, three times a day, for several weeks; for infants, 0.5mg (or 2.5mg) each time, twice a day is sufficient. At the same time, add a compound vitamin B supplement. If oral administration is not possible, B2 5-10mg can be injected intramuscularly once a day or a multivitamin preparation can be injected intravenously three times a day until oral administration is possible.

(2) For those with obvious glossitis symptoms, 50-100mg of niacin can be added daily; for those with obvious corneal lesions, a therapeutic dose of vitamin A can be added.

(3) Eat more foods rich in B2, such as liver, kidney, heart, etc.

(4) No cases of B2 poisoning have been found in humans or animals. However, there is an upper dose limit for B2 application, and exceeding this limit will not further increase B2 tissue levels.