Thumb nails with horizontal wrinkles may be caused by trauma, nail dystrophy, nail fungus disease, skin disease with nail damage and other factors. 1. Trauma: past history of local trauma, resulting in nail plate or nail bed damage, may appear nail with horizontal wrinkles. 2. Nail malnutrition: long-term partiality leads to a lack of micronutrients needed for nail growth, frequent manicure or long-term use of poor-quality detergents can lead to chemical corrosion of the nails, which can lead to changes in nail morphology, the appearance of transverse wrinkles-like manifestations. 3. Nail fungal disease: nail plate infected by fungi and other pathogens can trigger nail fungal disease, which can be manifested as nail morphology, color changes, and horizontal wrinkles can appear. 4. Skin disease with nail damage: when there is psoriasis, lichen planus and other inflammatory skin diseases, in addition to skin damage, can also be accompanied by the appearance of horizontal wrinkles and other nail morphology changes. When there are horizontal wrinkles on the thumbnail, you should consult a doctor in time and take active treatment under the guidance of a specialist.