Nail deformation refers to changes in the shape, hardness, thickness, and color of fingernails or toenails.

This condition has various names in classical medical texts. For example, Huangdi Neijing mentions "dry claws"; Zhubing Yuanhou Lun refers to "toe nail gangrene"; Waike Zhengzhi Quanshu describes "goose claws," "ingrown nails," "oil onychomycosis," as well as terms used by later physicians such as "spoon nails," "onycholysis," "oil-fried nails," "hook nails," "racket nails," and "spoon-shaped nails," all of which fall under the scope of this condition.

bubble_chart Pattern Analysis

1. Thick and Withered Nails︰Initially, there is itching at the distal or lateral edges of the fingernails or toenails, and in a few cases, it may start at the nail root. Over time, the surface becomes uneven, with yellowish stains appearing under the nail plate, gradually thickening or becoming hollowed out and incomplete. The edges of the nails thicken significantly, losing their original luster and turning grayish-white. The nail texture becomes brittle, crumbling into powder or developing gaps. The progression is slow, and many people also experience dampness between the toes, often without systemic symptoms. This condition is mostly caused by prolonged exposure to damp environments, immersion in water, or external invasion of damp toxins, which stagnate in the skin. Dampness is heavy, turbid, and lingering, making the onset slow and recovery difficult. It is often accompanied by dampness between the toes. The damage to the nails usually starts at the distal or lateral edges, gradually losing their luster, with the front edges thickening and spreading backward. Due to the obstruction of dampness, the qi and blood fail to nourish the nails, causing the nail plate to become brittle, develop yellow stains, or turn brownish or grayish-white and cloudy, with an uneven surface that eventually crumbles or becomes defective. Treatment should focus on dispelling dampness and wind, using vinegar-soaked formulas for soaking and washing. Internal treatment is generally unnecessary.
2. Nail Detachment︰It commonly occurs in the fingernails, initially appearing as whitening at the free edge and gradually spreading toward the nail root, turning grayish-white. The nails become softer than normal, lose their luster, and may affect one or multiple fingers, rarely the toes, often without systemic symptoms. This condition is mostly caused by excessive blood loss, deficiency of nutrient-blood, or inherent insufficiency of liver blood, leading to dryness of the liver channel's blood and failure to nourish the nails. The characteristic feature is the separation of the nail from the nail bed at the free edge, without itching or pain. In the early stages, the nails often become thin or soft, gradually turning grayish-white and hollow, lacking luster, which can be easily confused with thickened nails. However, the latter mainly involves nail thickening, and although it may become hollow in the late stage (third stage), careful observation can distinguish the two. Treatment should focus on nourishing liver blood and moisturizing the nails. The recommended formula is Jiawei Xiaoyao Wan.
3. Hook-shaped Nails︰The nail plate gradually thickens into a pointed, mountain-peak shape, reaching the size of a broad bean, with a rough surface appearing black, grayish-black, or greenish-black. As the nail plate grows, it curves forward or sideways into a hook-like shape, sometimes resembling an eagle's claw. The nail plate becomes opaque and loses its luster, often triggered by trauma, with few systemic symptoms. It mostly occurs after trauma or due to congenital factors, causing static blood to obstruct the collaterals, depriving the nail of nourishment, and thus gradually forming a hook-like shape. However, the thickening of the nail plate usually starts from the center and extends upward, forming a mountain-peak shape, which can thicken to about one centimeter. The tip curves forward like an eagle's claw, appearing black, bluish-black, or grayish-black, rarely brittle or powdery. Treatment should focus on {|###|}invigorating blood and resolving stasis{|###|}. The recommended formula is Origin-Restoring Blood-Invigorating Decoction.
4. Hook-shaped Nails︰It mostly occurs on the fingernails, and rarely on the toenails. The nail plate becomes thin and soft, with curled edges and a concave center, sometimes even spoon-shaped. It is often accompanied by palpitation, shortness of breath, dizziness, insomnia, sweating upon exertion, a pale complexion, and other symptoms. The tongue texture is pale, and the pulse manifestation is thin and weak. This condition often arises after a severe illness, in individuals with a weak constitution or inherent spleen and stomach deficiency, or those with a preference for the {|###|}five flavors{|###|}. People suffering from hunger and hardship may experience malnourishment of the nails, leading to thinning and softening of the nail plate, with edges curling up and the center becoming concave, presenting a spoon-like appearance. This is often accompanied by symptoms such as palpitation, shortness of breath, dizziness, insomnia, sweating upon exertion, and a pale complexion. Treatment should focus on {|###|}tonifying and replenishing qi and blood{|###|} and nourishing the nails. The recommended prescription is the Major Tonifying Pill.
5. Flat Nails︰The nail plate gradually becomes flattened with a cross-lined texture resembling a tennis racket, wide and flat at the top, accompanied by swelling of the nail groove and abnormal shortening of the distal phalanx. The tongue and pulse appear normal. This condition mostly occurs in infants and young children, often due to the bad habit of sucking or biting the thumb, which hinders the smooth circulation of qi and blood, leading to malnourishment of the nail plate and resulting in its flattened shape and shortened distal phalanx. Therefore, this condition is most commonly seen in the thumb, though it can also occur in the index finger. If the bad habit is corrected and dietary care is strengthened, the smooth circulation of qi and blood can be restored, leading to gradual recovery.

bubble_chart Documentation

1. Suwen．Five zang-organs Generation Theory: "Excessive consumption of pungent foods leads to tense sinews and withered nails."
2. 《Zhubing Yuanhou Lun》．Agnail Condition: "The peeling of skin at the edges of the nails on hands and feet is called 'inverse lu'. It is caused by wind evil entering the striae and interstice, leading to disharmony of blood and qi."
3. 《Zhubing Yuanhou Lun》．Toe Nail Gangrene Condition: "The condition of toe nail gangrene is characterized by thick, scaly, peeling skin on the nails. The sores are itchy and painful, often causing a desire to scratch, leading to discharge. Initially, it is caused by wind evil damaging the blood and qi, and there may also be worms inside."
4. 《Zhubing Yuanhou Lun》．Dai Zhi Condition: "Dai Zhi refers to the condition where the finger first swells, becomes hot and painful, and the color does not darken. Later, pus forms around the edge of the nail, and in severe cases, the nail falls off. It is also called Dai Jia, Zao Zhi, or Tu Zao. The nails are the surplus of the sinews. When the sinews and bones are excessively hot, and the qi is stagnant, swelling and pus formation occur, leading to the falling off of the nails."
5. 《Waike Zhengzhi Quanshu》．Volume 3: "Ingrown nail, where the nail suddenly grows into the flesh, causing stabbing pain like a needle, can be cured by eating sunflower leaves."
6. 《Waike Zhengzhi Quanshu》．Volume 3: "Goose claw wind, which is onychomycosis, can be treated by applying crushed white balsam flowers to the nails daily. When the balsam season passes, the gray nails will heal."