Biotin is generally considered safe for both oral and topical usage. However, one study based on food frequency questionnaires suggests that doses of biotin higher than 600 µg/day may increase risk of DNA damage. (63)
Potential Side Effects
Biotin helps keep your immune system healthy. However, there are some studies that suggest it may affect the immune system in ways that aren't beneficial to some people. (64)
However, experts caution that there's simply not enough evidence (yet) to predict harmful immune system effects from biotin. (65)
Can Biotin Cause Cystic Acne?
If you search for "does biotin cause pimples" on the internet you'll come across hundreds of sites with people complaining they took biotin (typically for hair loss) and suddenly had large, painful cystic acne-type of pimples appear on their face. However, an extensive search through medical journals and other scholarly material shows no such association.
Interestingly, people with cystic acne who use prescription retinoic acid (isotretinoin) to treat it have been known to develop biotin deficiency. Why? Because retinoic acid reduces levels of biotinidase, an enzyme needed to maintain biotin levels in the body. Biotin deficiency is associated with conditions such as hair loss, skin problems, and depression. (66)
Biotin is used in many cosmetic and personal care products for hair and skin, in concentrations ranging from 0.0001% to 0.6%. Tests show that while it does absorb some ultraviolet (UV) radiation, there does not appear to be any peaks in UVA or UVB, the types associated with skin damage. When used topically and orally, biotin is quickly metabolized and passed out of the body in urine. There has only been one report of hives as an adverse skin reaction. Based on available data of the large number of people exposed to biotin regularly with no adverse reactions, biotin is considered safe to use in cosmetic applications. (28)
Microgram; 1 µg is the equivalent of 1/1000 of a milligram..6
Peripheral blood mononuclear cells. (65)
Interleukin-1²(IL-1²) and interleukin-2. (65)