• Nail fungus. Onychomycosis, or nail fungal infection, is a leading cause of brittle nails. Fungi are parasitic microorganisms that can enter your nail through tiny cuts or spaces between the nail and the skin underneath it. Toenails are particularly susceptible to onychomycosis, since tight-fitting shoes provide a perfect environment for the fungi, which thrive where it is dark, moist and warm. Aside from causing crumbling and peeling nails, fungal infections can lead to discoloured and thickened nails.
• Psoriasis. Nail psoriasis affects approximately half of all people with skin psoriasis and the condition can cause lesions to form underneath the nail, resulting in split or misshapen nails. Pitted, loose, brittle and discoloured nails are other symptoms of nail psoriasis.    
• Trauma. Pinching a finger or smashing your toe can cause blood to pool underneath the nail, which can lead to a discoloured and brittle nail. Eventually, it may break away from the nail bed and fall off completely. If the nail bed is damaged as a result of the trauma, the new nail may not grow out correctly.
• Other diseases. In some cases, brittle nails are a sign of a more serious underlying medical condition, such as malnutrition, hyperthyroidism or other endocrine disorders.

If you have brittle, peeling or split nails mainly because of environmental factors, some simple lifestyle changes could help improve the problem. For example, avoid soaking your hands and feet in water for extended periods of time, and make sure to dry them thoroughly after they have been wet. Use a mild soap and do not wash your hands excessively. Also try to avoid exposing your nails to chemicals, such as harsh nail polish removers, and moisturize them daily.

But if a nail fungus or nail psoriasis is to blame for your dry and brittle nails, you will need additional treatment to get rid of the infection, and the sooner you start treatment the better. For mild to moderate cases of onychomycosis there are several over the counter creams, ointments and nail lacquers available. Another option is Naloc, a topical treatment that treats nails affected by fungal infection or psoriasis. It also improves the appearance of discoloured and deformed nails. Naloc increases hydration, gently smoothes the outer layers of the nail plate and, by changing the nail’s microenvironment and improving nail surface integrity, keeps nails in good condition. First signs of improvement are normally seen already after 2-4 weeks of treatment

For severe nail infections, a topical antifungal treatment may not suffice and your doctor may recommend oral medications, removal of the nail or laser treatment. Although there is no cure for nail psoriasis, severe cases are sometimes treated with steroid injections. 

Treating nail fungus and nail psoriasis is challenging and regardless of which treatment you choose, complete healing could take up to six months for a fingernail and a year for a toenail.