Onycholysis (ON) is a nail disorder characterized by the spontaneous detachment of the nail from its bed which starts from the tip and/or the sides  and moves progressively in a proximal direction.
In general, the nails affected by ON appear smooth, firm, and show no inflammatory reaction. When ON is triggered by a secondary infection, a characteristic discoloration can begin to appear which is clearly evident underneath the nail. As previously mentioned, ON follows a characteristic pattern. In the great majority of the cases the detachment starts from the distal free margin and moves progressively in the proximal direction, but sometime it might show the opposite movement, starting from the proximal border and moving towards the free edge. In general, the detachment interests the entire body of the nail, but in very rare cases it might involve just the lateral borders.
The diagnosis of ON is based on laboratory studies and histological findings. The laboratory studies are to be performed to exclude other causes of nail detachment, such as fungal infections like onychomycosis, well known to involve all the parts of the nail body and to cause serious physical and occupational limitations. The most important laboratory procedures include mycologic studies, potassium hydroxide test, particularly recommended to detect Candida infections, and general fungal cultures. Sometime these tests might give negative results, which have to be confirmed by additional procedures like nail biopsy, particularly useful to detect recalcitrant fungal infections  and obtain further diagnostic and prognostic information . Staining might also be useful, especially when hematoxylin and eosin are employed.
Histological findings might underline the presence of hyphae between the laminae of the nail running parallel to the surface, which particularly affect the ventral region of the nail and the stratum corneum. There might be episodes of spongiosis, that is an intracellular edema  all over the surface of the epidermis, together with a focal parakeratosis, which appears as a marked keratinization characterized by the retention of nuclei in the stratum corneum. Signs of inflammatory response are minimal, if not apparently totally absent.
The main goal of ON treatment is to eliminate its predisposing cause, and since there are many etiological factors for this condition, the treatment itself varies very much. However, the most important treatment in use is intralesional injection, especially when ON is associated with severe psoriatic nail dystrophy. Frequently used as injected drug is triamcinolone, which is first diluted in a solution of sodium chloride and then injected into the proximal nail fold generally in 4-6 sessions spaced out by intervals of 4 weeks each. The proximal nail fold is the ideal location for injection, even though the clinician might sometime use the nail bed, especially in the cases of changes due to onycholysis.
Fortunately enough, the nail changes are responsible for ON are not permanent and go away after that an appropriate clinical treatment have been performed. However, their disappearance is very slow, and it might take also several months for them to permanently disappear, even with the most effective treatment.
The most common cause of ON is trauma, particularly when it appears as a repetitive mechanical stress continuously exerting its force on the nail. For example, such a condition might present itself when the subject repetitively taps long fingernails on keyboards or counters on a daily basis, or when he/she overzealously manicures using tools with which he/she continuously pushes the nails from beneath causing them to lift and finally come away from their plate. Another typical “etiological situation” can be a prolonged immersion in water, in a condition in which the structure of the nail weakens to becomes easily exposed to damage by external forces.
Infection too is very important as etiological factor, inasmuch it frequently causes the tissue underneath the nail to thicken, and this in turn pushes the nail upwards until it breaks apart or comes away. The most common infectious factors include psoriasis, dermatophyte fungus, yeast (candida infection), and virus (herpes simplex infection). Furthermore, drugs can also be a frequent etiological factor, since they might sometime cause the nail to change its shape and contour, and this in the end leads to the final detachment of the nail. The main drugs causing ON include tetracyclines, fluoroquinolone antibiotics, a few contraceptives and some anti-cancer treatment.
Other etiological factors include impaired peripheral circulation, reaction to detergents like detergent-based shampoos or soaps, and hepatocellular dysfunctions which might develop marked changes, both on the nails of the hands and on the nails of the feet .
In summary, ON is caused by endogeneous and exogenous factors. The endogenous factors include:
The exogenous factors include:
The incidence of ON is unknown both in the US and in the rest of the world. There is no data regarding its distribution, although it has been observed in all races with no underlined predilection towards one racial group rather than another.
ON can present itself in both genders, even though many studies confirm a marked higher frequency of ON to manifest itself among females, perhaps due to the tendency of these to have long nails more subject to mechanical and physical stress. Furthermore, although ON can occur in people of any age, it is particularly frequent in adulthood, perhaps due to the higher number of risk factors that adults have faced over the year.
It should be remembered that ON is not a disease in itself, but rather a physiological condition which comes as a consequence or side effect of other underlying factors like traumas and infections. Therefore, an effective management, which avoids any further episode in the future, requires the treatment of these primary or secondary causes, that if left untreated could easily exacerbate the situation and lead to additional damage and further complications.
Avoiding those conditions which might cause episodes of ON is paramount for prevention of this disorder. Therefore, patients are strongly advised to follow some measures like:
Onycholysis (ON), the separation of the nail plate from the nail bed, can also occur on toes, although it is usually observed on the fingers of the hands, especially on the ring finger. The most common cause of ON is trauma , when the nail is pushed away from its bed by a mechanical stress that might also break and damage its body, but infections are also very frequent as etiological factors as they thicken the tissue immediately beneath the plate causing the edge of the nail to lift. ON is also frequently seen as side-effect of some disorder like psoriasis or hyperthyroidism, where ON is thought to be caused by an overactivity of the sympathetic nervous system .
Onycholysis (ON) is a nail disorder characterized by the spontaneous detachment of the nail from its bed starting from the tip and/or the sides and moving progressively towards the base of the nail itself. ON can also occur on toes, although it is usually observed on the fingers of the hands, especially on the ring finger.
The most common cause of ON in trauma, particularly when it appears as a repetitive mechanical stress continuously exerting its force on the nail. For example, such a condition might present itself when the affected individual repetitively taps long fingernails on keyboards or counters on a daily basis, or when he/she overzealously manicures using tools with which he/she continuously pushes the nails from beneath causing them to lift and finally come away from the plate. Another typical cause can be a prolonged immersion in water, in a condition in which the structure of the nail weakens to finally become easily exposed to damage by external forces. Infection is another common cause of ON, inasmuch it frequently causes the tissue underneath to thicken and push the nail upwards, as well as some drugs which might change the shape and contour of the nail causing its detachment. The main drugs associated with ON include several antibiotics, a few contraceptives and some anti-cancer treatment.
The major treatment for ON is intralesional injection with triamcinolone, usually injected into the proximal nail fold generally in 4-6 sessions spaced out by intervals of 4 weeks each. The proximal nail fold is the ideal location for the injection, even though the clinician might sometime use the nail bed if the clinical conditions require it.
The prevention of ON is based on a series of measures which include: