A darkened nail can mean a few things. First, it could be common to have streaks of the pigment melanin down your fingernails. Second, nail fungus infections can also have dark gray or green colors. But if there is a dark streak along the nail from cuticle to tip and there is only one, or it is changing fast, you should check by a doctor, as it may occasionally indicate a form of skin cancer called subungual melanoma, the most dangerous type of skin cancer.
If the nails are mostly white with darker rims, it could be an indication to a liver problem, like Hepatitis or Jaundice.
Most time pale nails are linked with aging, but very pale nails can sometimes be a sign of serious illness such as Anemia, Liver Disease, Malnutrition, Congestive Heart Failure and Diabetes.
In most of the cases yellow nails are caused due to a fungal infection, and as the infection becomes worse, the nail crumbles and the nail bed. In very rare cases, yellow nails can indicate a more serious condition such as severe thyroid disease, lung disease, diabetes or psoriasis.
The medical term of Blue fingernails is cyanosis. Most commonly, blue nails are the result of not getting enough oxygen. Normally, blood is bright red due to the oxygen it contains, but when oxygen levels decline, blood turns a blue-red color. This chronic cyanosis can be a sign of many different lung and breathing issues like asthma, emphysema, chronic obstructive pulmonary disease, chronic bronchitis and other respiratory disorders.
If the nail surface is rippled of the tip, it may be an early sign of ailments like Inflammatory Arthritis or Psoriasis. There are other conditions that can lead to this, such as autoimmune disorder or connective tissue issues.
Cracked or Split Nails
Brittle dry nails that frequently crack or split have been linked to thyroid disease. Cracking or splitting combined with a yellowish hue is more likely due to a fungal infection. Low levels of Vitamin C, folic acid, and certain proteins in the diet are also known to cause nail splitting.
Puffy Nail Fold
If the skin around the nail appears red and puffy, this case is known as inflammation of nail fold. Common infection can also cause redness and inflammation of the nail fold, but it might be caused due to the result of a connective or lupus tissue disorder.
Little Brown Streaks
These are thin dark lines under the fingernail that could be from mean tiny vessels under the nail that are bleeding. These are known as splinter hemorrhages. You are nothing to worry about if they are due to the nail being injured. However, if many nails are affected, this may be a sign that one of the heart valves is infected, known as “endocarditis”. Splinter hemorrhages can also be associated with several other conditions, such as scleroderma, lupus, psoriasis and rheumatoid arthritis.