Nails ridges are a symptom of iron deficiency, according to Everyday Health. People need iron in their blood to form hemoglobin, a protein that transports oxygen to the body's tissues, states Healthline. Iron deficiency commonly results from a poor diet.
Psoriasis, bacterial infections, anticancer chemotherapy and arsenic poisoning are other causes of nail ridges, reports HealthGrades. Horizontal ridges accompanied by nail discoloration often indicate more serious conditions.
Nails that are simply soft or brittle may result from keratin deficiency, which is treatable with Biotin, a vitamin B supplement. Chemicals such as acetone and methyl acrylate can also contribute to fragile nails, notes Everyday Health.