Most treatments are topical or oral antifungal medications.

Topical agents include ciclopirox nail paint, amorolfine or efinaconazole. Some topical treatments need to be applied daily for prolonged periods (at least 1 year). Topical amorolfine is applied weekly. Topical ciclopirox results in a cure in 6% to 9% of cases; amorolfine might be more effective. Ciclopirox when used with terbinafine appears to be better than either agent alone.

Oral medications include terbinafine (76% effective), itraconazole (60% effective) and fluconazole (48% effective). They share characteristics that enhance their effectiveness: prompt penetration of the nail and nail bed, persistence in the nail for months after discontinuation of therapy. Ketoconazole by mouth is not recommended due to side effects. Oral terbinafine is better tolerated than itraconazole. For superficial white onychomycosis, systemic rather than topical antifungal therapy is advised.

Chemical (keratolytic) or surgical debridement of the affected nail appears to improve outcomes.

As of 2014 evidence for laser treatment is unclear as the evidence is of low quality and varies by type of laser.

As of 2013 tea tree oil has failed to demonstrate benefit in the treatment of onychomycosis. A 2012 review by the National Institutes of Health found some small and tentative studies on its use.

There exist numerous treatments for nail psoriasis but there is little information concerning their effectiveness and safety.

Treatments include topical, intralesional, radiation, systemic, and combination therapies.

- Tacalcitol ointment obtains a significant improvement in all nail parameters, both of the matrix and of the bed.

- Clobetasol nail lacquer and tacalcitol ointment

- 5-fluorouracil. A reported side-effect is yellow nails

- Calcipotriol

- Calcipotriol plus betamethasone dipropionate ointment.

- Efalizumab

- Infliximab

- Golimumab

- Low dose methotrexate

- Intralesional corticosteroid injection

Available studies lack sufficient power to extrapolate a standardized therapeutic regimen.

As of April 2009, an assessment of the evidence for the efficacy and safety of the treatments for nail psoriasis is in progress.

- Infliximab appears to be the most effective treatment for nail psoriasis to date.

- Results from low-dose acitretin therapy show NAPSI score reductions comparable with those studies evaluating biologic drugs for nail psoriasis and suggest that low-dose systemic acitretin should be considered in the treatment of nail psoriasis.

In approximately half of suspected nail fungus cases there is actually no fungal infection, but only some nail dystrophy. Before beginning oral antifungal therapy the health care provider should confirm a fungal infection. Administration of treatment to persons without an infection is unnecessary health care and causes needless exposure to side effects.

Many different treatments have been reported for cutaneous lichen planus, however there is a general lack of evidence of efficacy for any treatment. Treatments tend to be prolonged, partially effective and disappointing. The mainstay of localized skin lesions is topical steroids. Additional treatments include retinoids, such as acitretin, or sulfasalazine. Narrow band UVB phototherapy or systemic PUVA therapy are known treatment modalities for generalized disease.

There is no cure for lichen planus, and so treatment of cutaneous and oral lichen planus is for symptomatic relief or due to cosmetic concerns. When medical treatment is pursued, first-line treatment typically involves corticosteroids, and removal of any triggers. Without treatment, most lesions will spontaneously resolve within 6–9 months for cutaneous lesions, and longer for mucosal lesions.

Most instances of onycholysis without a clear cause will heal spontaneously within a few weeks. The most commonly recommended treatment is to keep the nail dry as much as possible and allow the nail to slowly reattach. Trimming away as much loose nail as can be done comfortably will prevent the nail from being pried upwards. Cleaning under the nail is not recommended as this only serves to separate the nail further. Bandages are also to be avoided. When kept dry and away from further trauma, the nail will reattach from the base upward (i.e., from proximal to distal).

If the underlying cause of the condition is not found and the nail continues to detach despite conservative treatment, the nail bed may begin to form a granular layer of abnormal cells on its surface. After six months of detachment, this layer is likely to prevent the adhesion of any new nail tissue, possibly leading to permanent deformity.

When no pus is present, warm soaks for acute paronychia is reasonable, even though there is a lack of evidence to support its use. Antibiotics such as clindamycin or cephalexin are also often used, the first being more effective in areas where MRSA is common. If there are signs of an abscess (the presence of pus) drainage is recommended.

Chronic paronychia is treated by avoiding whatever is causing it, a topical antifungal, and a topical steroid. In those who do not improve following these measures oral antifungals and steroids may be used or the nail fold may be removed surgically.

Daily use of hand lotion or hand cream may help prevent the formation of hangnails.

For home treatment, the American Academy of Dermatology recommends washing the hands, clipping the loose piece of skin with a clean nail clipper or nail scissors, and applying over-the-counter antibiotic ointment if the area appears inflamed. Persistent hangnails should be evaluated by a physician.

Mild to moderate cases are often treated conservatively with warm water and epsom salt soaks, antibacterial ointment and the use of dental floss. If conservative treatment of a minor ingrown toenail does not succeed, or if the ingrown toenail is severe, surgical treatment may be required. A "gutter splint" may be improvised by slicing a cotton-tipped wooden applicator diagonally to form a bevel and using this to insert a wisp of cotton from the applicator head under the nail to lift it from the underlying skin after a foot soak.

Surgical treatment for an ingrown nail is carried out by a podiatrist, a foot and ankle specialist. This is typically an in-office procedure requiring local anesthesia and special surgical instruments. The surgical approach is the removal of the offending part of the nail plate known as a wedge resection. If the ingrown toenail recurs despite this treatment, destruction of the sides of the nail with chemicals or excision is done; this is known as a matrixcestomy. Antibiotics may be used after the procedure but are not recommended, as they may delay healing. Surgical treatment for ingrown nails is more effective at preventing the nail from regrowing inwards compared to non-surgical treatments.

Topical corticosteroid preparations are the most effective agents when used continuously for 8 weeks; retinoids and coal tar were found to be of limited benefit and may be no better than placebo. Greater benefit has been observed with very potent corticosteroids when compared to potent corticosteroids. Vitamin D analogues such as paricalcitol were found to be significantly superior to placebo. Combination therapy with vitamin D and a corticosteroid was superior to either treatment alone and vitamin D was found to be superior to coal tar for chronic plaque psoriasis.

Moisturizers and emollients such as mineral oil, petroleum jelly, calcipotriol, and decubal (an oil-in-water emollient) were found to increase the clearance of psoriatic plaques. Emollients have been shown to be even more effective at clearing psoriatic plaques when combined with phototherapy. However, certain emollients have no impact on psoriasis plaque clearance or may even decrease the clearance achieved with phototherapy. The emollient salicylic acid is structurally similar to para-aminobenzoic acid (PABA), commonly found in sunscreen, and is known to interfere with phototherapy in psoriasis. Coconut oil, when used as an emollient in psoriasis, has been found to decrease plaque clearance with phototherapy. Medicated creams and ointments applied directly to psoriatic plaques can help reduce inflammation, remove built-up scale, reduce skin turnover, and clear affected skin of plaques. Ointment and creams containing coal tar, dithranol, corticosteroids (i.e. desoximetasone), fluocinonide, vitamin D analogs (for example, calcipotriol), and retinoids are routinely used. The use of the finger tip unit may be helpful in guiding how much topical treatment to use.

Vitamin D analogues may be useful with steroids; however, alone have a higher rate of side effects. They may allow less steroids to be used.

Another topical therapy used to treat psoriasis is a form of balneotherapy, which involves daily baths in the Dead Sea. This is usually done for four weeks with the benefit attributed to sun exposure and specifically UVB light. This is cost-effective and it has been propagated as an effective way to treat psoriasis without medication. Decreases of PASI scores greater than 75% and remission for several months have commonly been observed. Side-effects may be mild such as itchiness, folliculitis, sunburn, poikiloderma, and a theoretical risk of nonmelanoma skin cancer or melanoma has been suggested. However, more recent studies have determined that there does not appear to be increased risk of melanoma in the long-term. Data are inconclusive with respect to nonmelanoma skin cancer risk, but support the idea that the therapy is associated with an increased risk of benign forms of sun-induced skin damage such as, but not limited to, actinic elastosis or liver spots. Dead Sea balneotherapy is also effective for psoriatic arthritis.

Phototherapy in the form of sunlight has long been used for psoriasis. Wavelengths of 311–313 nanometers are most effective, and special lamps have been developed for this application. The exposure time should be controlled to avoid over exposure and burning of the skin. The UVB lamps should have a timer that will turn off the lamp when the time ends. The amount of light used is determined by a person's skin type. Increased rates of cancer from treatment appear to be small. Narrow band UVB light (NBUVB) phototherapy has been demonstrated to have similar efficacy to PUVA.

One of the problems with clinical phototherapy is the difficulty many patients have gaining access to a facility. Indoor tanning resources are almost ubiquitous today and could be considered as a means for patients to get UV exposure when dermatologist provided phototherapy is not available. Indoor tanning is already used by many people as a treatment for psoriasis; one indoor facility reported that 50% of its clients were using the center for psoriasis treatment; another reported 36% were doing the same thing. However, a concern with the use of commercial tanning is that tanning beds that primarily emit UVA might not effectively treat psoriasis. One study found that plaque psoriasis is responsive to erythemogenic doses of either UVA or UVB, as exposure to either can cause dissipation of psoriatic plaques. It does require more energy to reach erythemogenic dosing with UVA.

UV light therapies all have risks; tanning beds are no exception, particularly in the link between UV light and the increased chance of skin cancer. There are increased risks of melanoma, squamous cell and basal cell carcinomas; younger psoriasis patients, particularly those under age 35, are at increased risk from melanoma from UV light treatment. The World Health Organization (WHO) listed tanning beds as carcinogens. A review of studies recommends that people who are susceptible to skin cancers exercise caution when using UV light therapy as a treatment.

A major mechanism of NBUVB is the induction of DNA damage in the form of pyrimidine dimers. This type of phototherapy is useful in the treatment of psoriasis because the formation of these dimers interferes with the cell cycle and stops it. The interruption of the cell cycle induced by NBUVB opposes the characteristic rapid division of skin cells seen in psoriasis. The activity of many types of immune cells found in the skin is also effectively suppressed by NBUVB phototherapy treatments. The most common short-term side effect of this form of phototherapy is redness of the skin; less common side effects of NBUVB phototherapy are itching and blistering of the treated skin, irritation of the eyes in the form of conjunctival inflammation or inflammation of the cornea, or cold sores due to reactivation of the herpes simplex virus in the skin surrounding the lips. Eye protection is usually given during phototherapy treatments.

Psoralen and ultraviolet A phototherapy (PUVA) combines the oral or topical administration of psoralen with exposure to ultraviolet A (UVA) light. The mechanism of action of PUVA is unknown, but probably involves activation of psoralen by UVA light, which inhibits the abnormally rapid production of the cells in psoriatic skin. There are multiple mechanisms of action associated with PUVA, including effects on the skin's immune system. PUVA is associated with nausea, headache, fatigue, burning, and itching. Long-term treatment is associated with squamous cell carcinoma (but not with melanoma). A combination therapy for moderate to severe psoriasis using PUVA plus acitretin resulted in benefit, but acitretin use has been associated with birth defects and liver damage.

Hangnails can become infected and cause paronychia, a type of skin infection that occurs around the nails. Treatments for paronychia vary with severity, but may include soaking in hot salty water, the use of oral antibiotic medication, or clinical lancing. Paronychia itself rarely results in further complications but can lead to abscess, permanent changes to the shape of the nail or the spread of infection.

Nail inspection can give hints to the internal condition of the body as well.

Nail disease can be very subtle and should be evaluated by a dermatologist with a focus in this particular area of medicine. A nail technician may be the first to note a subtle change in nail health.

Surgical excision is common and is a very effective mode of treatment.

Normal treatment for swelling and any respiratory problems is appropriate. Nutritional supplementation with Vitamin E in some studies has been shown to be effective in controlling nail changes.

The most common treatment, which is cheap and widely available, is to apply a clear, bitter-tasting nail polish to the nails. Normally denatonium benzoate is used, the most bitter chemical compound known. The bitter flavor discourages the nail-biting habit.

Behavioral therapy is beneficial when simpler measures are not effective. Habit Reversal Training (HRT), which seeks to unlearn the habit of nail biting and possibly replace it with a more constructive habit, has shown its effectiveness versus placebo in children and adults. A study in children showed that results with HRT were superior to either no treatment at all or the manipulation of objects as an alternative behavior, which is another possible approach to treatment. In addition to HRT, stimulus control therapy is used to both identify and then eliminate the stimulus that frequently triggers biting urges. Other behavioral techniques that have been investigated with preliminary positive results are self-help techniques, and the use of wristbands as non-removable reminders. More recently, technology companies have begun producing wearable devices and smart watch applications that track the position of users' hands.

Another treatment for chronic nail biters is the usage of a dental deterrent device that prevents the front teeth from damaging the nails and the surrounding cuticles. After about two months, the device leads to a full oppression of the nail biting urge.

Evidence on the efficacy of drugs is very limited and they are not routinely used. A small double-blind randomized clinical trial in children and adolescents indicated that N-acetylcysteine, a glutathione and glutamate modulator, could, in the short term only, be more effective than placebo in decreasing the nail-biting behavior.

Nail cosmetics can help to ameliorate nail biting social effects.

Independently of the method used, parental education is useful in the case of young nail biters to maximize the efficacy of the treatment programs, as some behaviors by the parents or other family members may be helping to perpetuate the problem. For example, punishments have been shown to be not better than placebo, and in some cases may even increase the nail biting frequency.

Periungual warts are warts that cluster around the fingernail or toenail. They appear as thickened, fissured cauliflower-like skin around the nail plate. Periungual warts often cause loss of the cuticle and paronychia. Nail biting increases susceptibility to these warts.

Warts of this kind often cause damage to the nail either by lifting the nail from the skin or causing the nail to partially detach. If they extend under the nail, then the patient may suffer pain as a result. Sometimes periungual wart infections resemble the changes that are found in onychomycosis. In worst cases, if the infection causes injury or damage to the nail matrix, deformity in the nail may become permanent.

As with other wart types, a number of treatments are available, including laser therapy, cryotherapy, salicylic acid, and other topical treatments.

Subungual hematomas are treated by either releasing the pressure conservatively when tolerable or by drilling a hole through the nail into the hematoma (trephining), or by removing the entire nail. Trephining is generally accomplished by using a heated instrument to pass through the nail into the blood clot. Removal of the nail is typically done when the nail itself is disrupted, a large laceration requiring suturing is suspected, or a fracture of the tip of the finger occurs. Although general anesthesia is generally not required, a digital nerve block is recommended to be performed if the nail is to be removed.

Subungual hematomas typically heal without incident, though infection or disruption of the nail (onycholysis) may occur.

Chronic exposure to human nail dust is a serious occupational hazard that can be minimized by not producing such dust. Best practice is to avoid electrical debridement or burring of mycotic nails unless the treatment is necessary. When the procedure is necessary, it is possible to reduce exposure by using nail dust extractors, local exhaust, good housekeeping techniques, personal protective equipment such as gloves, glasses or goggles, face shields, and an appropriately fitted disposable respirators to protect against the hazards of nail dust and flying debris.

Longitudinal erythronychia presents with longitudinal red bands in the nail plate that commence in the matrix and extend to the point of separation of the nail plate and nailbed, and may occur on multiple nails with inflammatory conditions such as lichen planus or Darier's disease.

There have been numerous accounts of patients with "trichophyton" fungal infections and associated asthma, which further substantiates the likelihood of respiratory disease transmission to the healthcare provider being exposed to the microbe-laden nail dust In 1975, a dermatophyte fungal infection was described in a patient with severe tinea. The resulting treatment for mycosis improved the patient’s asthmatic condition. The antifungal treatment of many other "trichophyton" foot infections has alleviated symptoms of hypersensitivity, asthma, and rhinitis.

"Onycholysis" is from "onycho-", from Ancient Greek ὄνυξ "ónuks", meaning "nail", and Ancient Greek λύσις "lúsis", meaning "a loosening".