Pseudomonas aeruginosa is a common bacterium that can cause disease in animals, including humans. It is found in soil, water, skin flora, and most man-made environments throughout the world. It thrives not only in normal atmospheres, but also in hypoxic atmospheres, and has, thus, colonized many natural and artificial environments. It uses a wide range of organic material for food; in animals, the versatility enables the organism to infect damaged tissues or those with reduced immunity. The symptoms of such infections are generalized inflammation and sepsis. If such colonizations occur in critical body organs, such as the lungs, the urinary tract, and kidneys, the results can be fatal. Because it thrives on most surfaces, this bacterium is also found on and in medical equipment, including catheters, causing cross-infections in hospitals and clinics. It is implicated in hot-tub rash. It is also able to decompose hydrocarbons and has been used to break down tarballs and oil from oil spills.

Green nails may be (1) due to a "Pseudomonas aeruginosa" infection causing a green nail syndrome or (2) the result of copper in tap water.

A 2003 survey of diseases of the foot in 16 European countries found onychomycosis to be the most frequent fungal foot infection and estimates its prevalence at 27%. Prevalence was observed to increase with age. In Canada, the prevalence was estimated to be 6.48%. Onychomycosis affects approximately one-third of diabetics and is 56% more frequent in people suffering from psoriasis.

Advice often given includes:

- Avoid sharing clothing, sports equipment, towels, or sheets.

- Wash clothes in hot water with fungicidal soap after suspected exposure to ringworm.

- Avoid walking barefoot; instead wear appropriate protective shoes in locker rooms and sandals at the beach.

- Avoid touching pets with bald spots, as they are often carriers of the fungus.

Following effective treatment recurrence is common (10–50%).

Nail fungus can be painful and cause permanent damage to nails. It may lead to other serious infections if the immune system is suppressed due to medication, diabetes or other conditions. The risk is most serious for people with diabetes and with immune systems weakened by leukemia or AIDS, or medication after organ transplant. Diabetics have vascular and nerve impairment, and are at risk of cellulitis, a potentially serious bacterial infection; any relatively minor injury to feet, including a nail fungal infection, can lead to more serious complications. Infection of the bone is another rare complication.

no approved human vaccine exist against "Dermatophytosis". For horses, dogs and cats there is available an approved inactivated vaccine called "Insol Dermatophyton" (Boehringer Ingelheim) which provides time-limited protection against several trichophyton and microsporum fungal strains.

Fungi are ubiquitous organisms that play a vital role in decomposing organic matter. Many species of fungi live on the human body and some will infect nails causing a condition called onychomycosis. There are oral and topical antifungal therapies for this condition, however, in some instances cutting, filing, or abrading the nail may be necessary to improve cure rates. Thickened nails caused by injury, infection, diabetes, psoriasis, or vascular disease may require the use of a mechanical therapy, which can expose the healthcare worker to microbial dust.

Exposure to nail dust was first discussed and described in the literature as an occupational hazard in the early 70’s. In 1975, two female chiropodists were diagnosed with allergic hypersensitivity to nail dust Since that time, there have been a number of occupational-related complaints pertaining to airborne nail dust exposure and efforts have been made to study the podiatric professionals to determine related symptoms. Biological dust from the hand and foot care procedures may deposit in the conjunctiva, nose, and throughout the respiratory tract. The local irritation of these areas can lead to conjunctivitis, itching, tearing, rhinitis, sneezing, asthmatic attacks, bronchitis, and coughing.

The literature suggests that nail dust can be a respiratory sensitizer, which is defined as a substance that when breathed in can trigger an irreversible allergic reaction in the respiratory system. Sensitization does not usually take place immediately, but rather after months or years of exposure to the agent. Once sensitized, even the smallest amount of the substance can trigger asthma, rhinitis, or conjunctivitis that may exhibit the following symptoms: coughing, wheezing, chest tightness, runny or stuffy nose, and watery or prickly eyes. Millar found that within the podiatry profession there is four times the national prevalence of asthma. Hypersensitivity reactions are the most probable disposition for healthcare workers inhaling nail dust, although more serious lung pathology can not be ruled out

It is widely known and accepted that fungi will induce asthma, but it is estimated that only 10% of the population has allergic antibodies to fungal antigens, and half of them, that is 5% of the population, would be asymptomatic, further complicating the link between the fungal dust and troubling symptoms. "Trichophyton rubrum" is the most common fungal cause of nail dystrophy. Studies conducted in England found that the prevalence of "trichophyton rubrum" antibodies in podiatrists ranged from 14%-31%. This is evidence that the podiatrist is heavily exposed to "trichophyton rubrum" as observed in increased precipitating antibodies compared to the general population. It has been suggested that absorption of "trichophyton" fungal antigens can give rise to immunoglobulin E (IgE) antibody production, sensitization of the airways, and symptomatic asthma and rhinitis.

Nail work requiring clipping and drilling is also a potential cause for ocular injury and infection to the podiatrists, podiatric staff, and patients that are exposed to nail fragments and high-speed drills used for grinding. Possible ocular hazards result from exposure to foreign bodies, allergens, bacteria, viruses, fungi and protozoa that can be introduced at the time of eye trauma, or enter as a consequence of damage to the ocular structures; permitting the entry of opportunistic infection. The high-speed rotation of podiatry drill burrs potentially expose the healthcare worker to aerosols containing bloodborne pathogens such as Hepatitis B, Hepatitis C, or HIV. Davies et al. surveyed podiatrists and found that 41% of them complained of eye problems, particularly soreness, burning, itching and excess lacrimation.

A 1990 case illustrates the potential for ocular trauma to the healthcare provider: A podiatrist suffered a lacerated cornea when hit by a metallic shard from the grinding bit or by a fragment from the patient’s toenail. The podiatrist reported fleeting periods of blurriness for several months following the incident. The healthcare worker’s exposure to foreign bodies is not well documented in the literature like they are with dental staff using similar equipment; however, many of these incidents are certain to go unreported. The healthcare provider’s risk of injury during nail care, however slight, warrants the use of simple and inexpensive preventative measures.

The most common digit to become ingrown is the big toe, but ingrowth can occur on any nail. Ingrown nails can be avoided by cutting nails straight across; not along a curve, not too short and no shorter than the flesh around it. Footwear that is too small or too narrow, or with too shallow of a "toe box", will exacerbate any underlying problem with a toenail. Sharp square corners may be uncomfortable and cause snagging on socks. Proper cutting leaves the leading edge of the nail free of the flesh, precluding it from growing into the toe. Filing of the corner is reasonable. Some nails require cutting of the corners far back to remove edges that dig into the flesh; this is often done as a partial wedge resection by a podiatrist. Ingrown toe nails can be caused by injury, commonly blunt trauma in which the flesh is pressed against the nail causing a small cut that swells. Injury to the nail can cause it to grow abnormally, making it wider or thicker than normal, or even bulged or crooked.

Peach scab, also known as peach freckles, is a disease of stone fruits caused by the fungi "Cladosporium carpophilum". The disease is most prevalent in wet and warm areas especially southern part of the U.S. as the fungi require rain and wind for dispersal. The fungus causes scabbing, lesions, and defoliating on twig, fruit, and leaf resulting in downgrade of peach quality or loss of fruits due to rotting in severe cases.

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.

The main contributor to onychocryptosis is footwear, particularly ill-fitting shoes with inadequate toe-box room and tight stockings that apply pressure to the top or side of the foot. Other factors may include the damp atmosphere of enclosed shoes, which soften the nail-plate and cause swelling on the epidermal keratin (eventually increasing the convex arch permanently), genetics, trauma and disease. Improper cutting of the nail may cause the nail to cut into the side-fold skin from growth and impact, whether or not the nail is truly "ingrown". The nail bends inwards or upwards depending on the angle of its cut. If the cutting tool, such as scissors, is at an attitude in which the lower blade is closer to the toe than the upper blade, the toenail will tend to grow upwards from its base, and vice versa. The process is visible along the nail as it grows, appearing as a warp advancing to the end of the nail. The upper corners turn more easily than the center of the nail tip. Holding the tool at the same angle for all nails may induce these conditions; as the nail turns closer to the skin, it becomes harder to fit the lower blade in the right attitude under the nail. When cutting a nail, it is not just the correct angle that is important, but also how short it is cut. A shorter cut will bend the nail more, unless the cut is even on both top and bottom of the nail.

Causes may include:

- Shoes causing a bunching of the toes in the developmental stages of the foot (frequently in people under 21), which can cause the nail to curl and dig into the skin. This is particularly the case in ill-fitting shoes that are too narrow or too short, but any toed shoes may cause an ingrown nail.

- Poor nail care, including cutting the nail too short, rounded off at the tip or peeled off at the edges instead of being cut straight across.

- Broken toenails.

- Trauma to the nail plate or toe, which can occur by dropping objects on or stubbing the toenail, or by the nail protruding through the shoe (as during sports or other vigorous activity), can cause the flesh to become injured and the nail to grow irregularly and press into the flesh.

- Predisposition, such as abnormally shaped nail beds, nail deformities caused by diseases or a genetic susceptibility, increases the chance of an ingrown nail, but the ingrowth cannot occur without pressure from a shoe.

- A bacterial infection, treatable with antibiotics.

One study compared patients with ingrown toenails to healthy controls and found no difference in the shape of toenails between those of patients and of the control group. The study suggested that treatment should not be based on the correction of a non-existent nail deformity. Ingrown toenails are caused by weight-bearing (activities such as walking, running, etc.) in patients that have too much soft skin tissue on the sides of their nail. Weight bearing causes this excessive amount of skin to bulge up along the sides of the nail. The pressure on the skin around the nail results in the tissue being damaged, resulting in swelling, redness and infection. Many treatments are directed at the nail itself and often include partial or full removal of the healthy nail. However, failure to treat the cutaneous condition can result in a return of the ingrowth and a deformity or mutilation of the nail.

Green nail syndrome, also known as chloronychia, is a paronychial infection caused due to "Pseudomonas aeruginosa" that can develop in individuals whose hands are frequently submerged in water. It may also occur as transverse green stripes that are ascribed to intermittent episodes of infection.

Disseminated protothecosis is most commonly seen in dogs. The algae enters the body through the mouth or nose and causes infection in the intestines. From there it can spread to the eye, brain, and kidneys. Symptoms can include diarrhea, weight loss, weakness, inflammation of the eye (uveitis), retinal detachment, ataxia, and seizures.

Dogs with acute blindness and diarrhea that develop exudative retinal detachment should be assessed for protothecosis. Diagnosis is through culture or finding the organism in a biopsy, cerebrospinal fluid, vitreous humour, or urine. Treatment of the disseminated form in dogs is very difficult, although use of antifungal medication has been successful in a few cases. Prognosis for cutaneous protothecosis is guarded and depends on the surgical options. Prognosis for the disseminated form is grave. This may be due to delayed recognition and treatment.

Leukonychia (or leuconychia), also known as white nails or milk spots, is a medical term for white discolouration appearing on nails. It is derived from the Greek words "leuko" ("white") and "nychia" ("nails"). The most common cause is injury to the base of the nail (the matrix) where the nail is formed.

It is harmless and most commonly caused by minor injuries, such as nail biting, that occur while the nail is growing. Leukonychia occurs most commonly in healthy individuals, unrelated to any known nutritional or physiological deficiency. When caused by injury the marks will disappear as the nail grows outwards, however a dietary deficiency will cause recurrent leukonychia.

Other possible reasons for this problem with nail colour can be linked to:

- Arsenic poisoning

- Lead poisoning

- Pneumonia

- Heart disease

- Renal failure

- Ill health

- Hypoalbuminemia

- Vitamin deficiency

- Ulcerative colitis

- Hepatic cirrhosis

- Psychogenic stresses

- Onychophagia

- Occupational trauma

- Zinc deficiency

- Protein deficiency

- Psoriasis as well as eczema

- Iron deficiency

Due to the effectiveness of fungicide application and it’s relatively minor damage to crops, there are few cultural controls and no resistant peach variants that have been developed for the current market. For prevention of peach scab, proper pruning of leaves to allow adequate sunlight will drastically reduce the risk of infection and propagation. The primary form of regulation for peach scab requires frequent applications of commercial fungicides. There are three main types of fungicides that are effective against peach scab: captan, chlorothalonil, and demethylation inhibitors. Proper use of chlorothalonil requires application starting from shuck split and reapplication every two weeks. Increased temperature and wet weather will necessitate more frequent applications. Applications are necessary until 4–6 weeks until harvest.

Cattle can be affected by protothecal enteritis and mastitis. Protothecal mastitis is endemic worldwide, although most cases of infected herds have been reported in Germany, the United States, and Brazil.

Flystrike in sheep is a myiasis condition, in which domestic sheep are infected by one of several species of flies which are external parasites of sheep.

The most widely used potassium fertilizer is potassium chloride (muriate of potash). Other inorganic potassium fertilizers include potassium nitrate, potassium sulfate, and monopotassium phosphate. Potassium-rich treatments suitable for organic farming include feeding with home-made comfrey liquid, adding seaweed meal, composted bracken, and compost rich in decayed banana peels. Wood ash also has high potassium content. Adequate moisture is necessary for effective potassium uptake; low soil water reduces K uptake by plant roots. Liming acidic soils can increase potassium retention in some soils by reducing leaching; practices that increase soil organic matter can also increase potassium retention.

Potassium deficiency, also known as potash deficiency, is a plant disorder that is most common on light, sandy soils, because potassium ions (K) are highly soluble and will easily leach from soils without colloids. Potassium deficiency is also common in chalky or peaty soils with a low clay content. It is also found on heavy clays with a poor structure.

This condition is a whitening of the entire nail. This may be a clinical sign of hypoalbuminaemia (low albumin), which can be seen in nephrotic syndrome (a form of kidney failure), liver failure, protein malabsorption and protein-losing enteropathies. A genetic condition, and a side effect of sulphonamides (a family of antibiotics) can also cause this appearance.

Fly strike in sheep is a condition where parasitic flies lay eggs on soiled wool or open wounds. After hatching, the maggots, bury themselves in the sheep’s wool and eventually under the sheep’s skin, feeding off their flesh. Once the larvae develop, flies continue to deposit eggs on to new or already infected sheep, starting the infection process over again. Sheep display symptoms such as agitation, odour and matted wool, all which further encourage the attraction of flies. Fly strike can be lethal for sheep due to ammonia poisoning.

Fly strike is problematic, not only causing loss or degradation of stock, but also requiring expenditure of both money and time for effective management. In Australia, "Lucilia cuprina" causes about 90% of infestations, and "Chrysomya rufifacies" is the most common secondary pest the targets wounds caused by "L. cuprina".

Endothrix refers to dermatophyte infections of the hair that invade the hair shaft and internalize into the hair cell. This is in contrast to exothrix (ectothrix), where a dermatophyte infection remains confined to the hair surface. Using an ultraviolet Wood's lamp, endothrix infections will not fluoresce whereas some exothrix infections may fluoresce bright green or yellow-green.

Fertilisers like ammonium phosphate, calcium ammonium nitrate, urea can be supplied. Foliar spray of urea can be a quick method.

All plants require sufficient supplies of macronutrients for healthy growth, and nitrogen (N) is a nutrient that is commonly in limited supply. Nitrogen deficiency in plants can occur when organic matter with high carbon content, such as sawdust, is added to soil. Soil organisms use any nitrogen to break down carbon sources, making N unavailable to plants. This is known as "robbing" the soil of nitrogen. All vegetables apart from nitrogen fixing legumes are prone to this disorder.

Nitrogen deficiency can be prevented in the short term by using grass mowings as a mulch, or foliar feeding with manure, and in the longer term by building up levels of organic matter in the soil. Sowing green manure crops such as grazing rye to cover soil over the winter will help to prevent nitrogen leaching, while leguminous green manures such as winter tares will fix additional nitrogen from the atmosphere.

Onychorrhexis (from the Greek words ὄνυχο- "ónycho-", "nail" and ῥῆξις "rhexis", "bursting"), also known as brittle nails, is a brittleness with breakage of finger or toenails that may result from excessive strong soap and water exposure, nail polish remover, hypothyroidism, anemia, anorexia nervosa or bulimia, or after oral retinoid therapy. Onychorrhexis affects up to 20% of the population.