Hyaluronic acid (HA) supplements are popular for supporting skin hydration, joint lubrication, and eye health, available as capsules, liquids, or combined with other ingredients like collagen and MSM, with most people finding them safe for oral use, though side effects like rare allergic reactions or irritation can occur, and consistent use (weeks) is needed for results, especially for skin benefits. They work by attracting and holding water, acting as a cushion and lubricant in joints and tissues, and are used for dry eyes, skin aging, and osteoarthritis.