Vitamin B complex, which includes biotin (B7), niacin (B3), pantothenic acid (B5), and others, is commonly associated with hair health. Among these, biotin is the most studied in relation to hair growth, and its supplementation is often recommended for individuals with hair thinning or hair loss. Scientific evidence primarily supports the use of vitamin B supplements in cases where hair loss is due to an underlying deficiency. For example, biotin deficiency, though rare in individuals with a balanced diet, can lead to hair thinning and loss, and supplementation reverses these effects. However, in individuals without a deficiency, robust clinical evidence demonstrating that B vitamins (including biotin) significantly enhance hair growth or prevent hair loss is lacking. Some observational studies and case reports suggest a potential benefit, but large, well-controlled clinical trials are limited. Other B vitamins, such as B12 and folate, contribute to overall cell health, including that of hair follicles, but direct links to hair growth are not strongly established in scientific literature. In summary, the use of vitamin B for hair support is justified by scientific evidence mainly in cases of deficiency; for the general population without deficiencies, the benefit is less certain and not firmly established by high-quality studies.