B-complex vitamins are largely composed of eight key nutrients, including B1 or thiamine that help convert nutrients to energy; B2 or riboflavin that acts as an antioxidant; B3 or niacin that works on cellular signaling and metabolism; B5 or pantothenic acid that is involved in energy, hormone and cholesterol production; B6 or pyridoxine that aids red blood cell production; B7 or biotin that regulates gene expression and helps carbohydrate and fat metabolism; B9 or folate that is needed for cell growth, among many other things; and B12 that is vital for healthy neurological function.

This product is allergen-free. Pure Encapsulations

Allergies to B vitamins are extremely rare, but in some cases have been known to cause itching and swelling around the face, tongue, and throat, severe dizziness, and asthma-lung respiratory symptoms. Many brands have developed formulations free to magnesium stearate, gluten, hydrogenated fat, artificial sweeteners and colors, GMOs, soy, and animal products like milk and eggs, to limit these reactions in the event that the allergies are connected to those ingredients.

B-complex vitamins generally work well with other medications—there are few negative interactions—but patients should consult their doctor or trusted medical adviser before starting a supplement regimen. Blood pressure and chemotherapy drugs, antiseizure meds and some antibiotics can result in low levels of some specific B vitamins. In those cases, B-complex supplements can be a good addition.

This product is geared for stronger, healthier hair. Zhou Nutrition

Some studies have suggested that B-complex and B-complex vitamin blends may help with hair and nail growth. B7 or biotin is thought to promote healthy hair growth and coupled with additives like collagen and keratin it may promote richer, fuller, straighter hair, but the scientific literature on this is mixed. Many hair-specific B-complex manufacturers suggest at least four weeks of supplementation before gauging results.