Ayurveda defines Nail as a waste product of the Bones as per the historic texts it is Asthi Dhatu. Nail defines your Dosha and Imbalance like tongue.
Discoloration of the nail bed, Split and flaky nails, Vertical ridges, White spots
Nail help diagnose Bone health, Malabsorption, Lung issues, Heart issues, Metabolic conditions, Inflammation, Parasites, Psoriasis and other skin disorders, Autoimmune conditions such as Lupus (SLE) and alopecia, Thyroid issues (hypo or hyper), Digestive issues, GI tract issues, Liver issues, Vata, Pitta or Kapha disorder, Vata, Pitta or Kapha constitution (not by itself, but used as a helpful indicator)
Kapha Dosha Square shape, white in color, thick and large.
Pitta Dosha Oval shape, Soft, Strong and flexible.
Vata Dosha Irregular shape, Pale, Rough and Brittle.