Likely causes such as micro-trauma (or overt trauma), forms of eczema such as irritants (a form of micro-trauma), allergies (allergic to something), xerosis (dry skin) and nutritional/vitamin deficiencies are the major causes and have all been mentioned. Each is a little different and although they can overlap, each cause will require a different treatment. Therefore it will probably be necessary for an evaluation by a dermatologist. In the meantime: 1. meticulous care to protecting the hands/nails , if you use your hands a lot at home or at work, think about how you can decrease 'wear and tear'. This may require wearing cotton gloves or keeping hands out of wet environments. 2. think about exposures that could be causing irritation or allergies - do certain things make your hands worse, are there any chemicals or drying agents that could be responsible? Consider nail polish and nail enhancement treatments (artificial or acrylic nails) - these are often causes. Try to avoid for a 3-4 weeks and see if there is improvement. 3. Use a heavy emollient or cream and massage around the nail and cuticles at least twice a day. Vaseline and Aquaphor are often helpful as are creams like CeraVe. For more difficult cases a OTC cortisone ointment is a nice substitute. Putting gloves (vinyl or cotton) over the medication or emollients are helpful at night. (wear overnight or for at least an hour). 4. Try zinc oxide topically and biotin supplements orally. 5. See your dermatologist - who is a specialist in nail disorders. :)