Onychoschizia, also known as nail splitting and brittle nails, is a splitting of the free-edged tip of the nail.[1] There is also often a longitudinal split in addition to the separation of keratin layers.[2]
Frequent hand-washing is the usual cause, but it is also part of normal ageing.[3] Manicures, nail polish and remover, nail biting, and repeated trauma such as typing, can contribute to nail splitting.[1] Dehydration likely plays a role.[3] Nutritional deficiencies that can result in nail splitting include iron, selenium, and zinc.[1] Some skin diseases such as psoriasis and lichen planus may feature such nails.[3]
Diagnosis is by its appearance, but sometimes blood tests are required to look for iron deficiency, thyroid problems, and kidney problems.[1]
Treatment is by discontinuing nail polish and applying moisturiser.[2] An acceptable alternative is gel nails.[2] Some favourable response has been reported with biotin if the person is deficient in vitamin B7.[1] It is not routinely given.[1]
It is common among women and occurs in almost a third of newborns.[2]
It also occurs in hooved animals such as horses.[4]
