The exact cause of psoriasis is unknown. It is thought that psoriasis develops in people who have an inherited tendency for the immune system in their skin to react abnormally to certain environmental conditions.

Psoriasis is more common in people who have relatives with psoriasis. The condition affects all racial groups and affects about 2% of people worldwide.

Psoriasis may be triggered for the first time by infections such as streptococcal tonsillitis, HIV and other viral infections as well as by severe emotional stress. Psoriasis is not contagious.

Smoking and excessive alcohol intake may worsen the condition.

Some medications may trigger psoriasis or cause psoriasis to become more severe. These medications include lithium, beta-blockers, anti-malarial medication, and rapid withdrawal of systemic corticosteroids.

Irritant contact dermatitis

The most common form of OCD is irritant contact dermatitis. This is caused when an irritant contacts the skin for a sufficiently long enough time to damage the skin cells. Often there is exposure to multiple irritants at the same time. Wet work, with successive wetting and drying of the skin, is the most common cause of irritant contact dermatitis. People with a background of atopic eczema often have a more easily damaged skin barrier and are at increased risk of irritant contact dermatitis. Other causes of irritant contact dermatitis are harsh soaps, solvents, oils, and physical factors such as heat, sweating and friction. Once the skin barrier is damaged with irritant contact dermatitis, there is an increased risk of developing allergic contact dermatitis.

Allergic contact dermatitis

Allergic contact dermatitis occurs when an allergen penetrates the skin and combines with the skin immune cells. The allergen (sometimes referred to as the sensitiser) then moves to the lymph glands where they react with T-lymphocytes which produce cells which remember the particular allergen. The next time the allergen contacts the skin, this will result in a rash, known as allergic contact dermatitis. Only certain small chemicals have the capability to cause allergic contact dermatitis. Common occupational causes include rubber accelerators in rubber products, especially in protective gloves, preservatives in skincare products, workplace chemicals and paints, chromate in cement and leather, hairdressing chemicals and epoxy resins.

Contact urticaria

Contact urticaria is another form of allergy which happens almost immediately on skin contact with an allergen (usually within 10-30 minutes). It can cause hay fever-like symptoms or asthma, as well as skin reactions. Contact urticaria is diagnosed by skin prick-testing or a blood test. Common causes include latex, hairdressing bleach (ammonium persulphate) and some foods contacted by food handlers.

There are several conditions that can affect our nails, with different causes and treatments.

Nail discolouration

The healthy nail plate is pink, and the nail looks white as it grows off the nail bed. Causes of discoloured nails typically include:

• Nail polish
• Nicotine from cigarette smoking
• Hair-colouring agents
• Certain infections
• Injury to the nail bed
• Some medications, including antibiotics, anti-malarial medications, and some medications used in chemotherapy
• Melanoma

Lifted nail plate

If the nail plate lifts off the nail bed, it will appear white. Common causes include:

• Overzealous cleaning under the fingernails
• Nail polishes that contain hardening chemicals such as formalin
• Rough removal of artificial nails
• Psoriasis
• Tinea

Thickened nails

This condition affects the toenails more than the fingernails. Older people are at greater risk. Causes include:

• Fungal infection
• Neglect
• Injury
• Poor circulation
• Arthritis in the toes
• Altered gait (walking) pattern
• Ill-fitting shoes
•  

Ridged nails

Ridges running either the length or width of the nail plate can have a number of causes, including:

• Age-related changes
• Trauma to the nail matrix
• Overzealous attention to the cuticles
• Fever or illness
• Eczema
• Rheumatoid arthritis
• Peripheral vascular disease
• Lichen planus infection.

Splitting nails

In this condition, the nail plate splits or layers as it grows off the nail bed. Common causes include:

• Having constantly wet hands, especially while using soap and washing detergents
• Frequently using and removing nail polish
• Continuous mild trauma such as habitual finger-tapping or using the nails as tools (to pick between the teeth, for example).

Deformed or brittle nails

Trauma can injure the nail bed and cause the nail to grow in a deformed way. The nail may be thickened or ridged. It is a normal ageing process for nails to thicken.

Deformed or brittle toenails can benefit from regular professional attention. Trimming, shaping and nail care from a podiatrist can improve the health of your toenails and help diagnose and treat more serious nail problems.

Bacterial infection of the nail

The Staphylococcus aureus bacterium is a common cause of bacterial infection of the nail. Typically, the infection first takes hold in the fold of skin at the base of the nail (proximal nail fold). Without treatment, the infection can worsen, leading to inflammation and pus. It is often associated with candida infection, particularly when it becomes chronic.

Activities that predispose a person to a bacterial nail infection include:

• Having constantly wet hands
• Overzealous attention to the cuticles
• Severe nail biting, which can expose underlying tissues to infection
• Eczema around the fingernails.

Inflammation of the skin alongside the nail – paronychia

The skin lying alongside the nail can become infected with bacteria, typically Staphylococcus aureus. This infection is called paronychia. Symptoms may include pain, redness and swelling around the cuticle and yellow-green discharge.

Treatment for paronychia includes:

• Keeping your feet as dry as possible
• Use of barrier creams, antiseptic lotions and antifungal preparations
• Antibiotic therapy (in acute cases).

Fungal infection

Fungal infections, such as tinea, are spread from one person to another and can affect the fingernails or toenails. Without treatment, the nail bed itself can become infected. People with diabetes or with compromised immune systems are at higher risk of fungal infection.
Treatment for fungal infection includes:

• Antifungal preparations applied topically (directly to the nail) or taken orally (by mouth)
• Professional trimming, shaping and care of the toenail by your podiatrist.

Trauma to the nail

A blow to the nail or compulsive nail biting can cause a range of problems, including:

• Bruising of the nail bed
• Lifting of the nail plate
• Loss of the nail plate
• Nail ridges
• Deformed growth of the nail plate if the nail matrix is injured.

Ingrown toenail

One of the most common problems treated by podiatrists is ingrown toenails. The big toe is particularly prone to this painful condition. Causes may include:

• Incorrect nail-trimming technique
• Trauma (such as stubbing your toe)
• Nails that naturally curve sharply on the sides and dig into the skin
• Wearing tight shoes.

Skin diseases and nails

Skin diseases such as psoriasis, eczema (dermatitis), lichen planus or lupus can affect the nails. Abnormalities may include pits, grooves or crumbling nails.

Unusual nail shape

Unusual nail shape – such as the nails becoming concave – can be caused by iron deficiency.

Nail tumours

Nails can be affected by tumours – including squamous cell carcinoma, usually caused by infection with the human papillomavirus (HPV). Melanoma can also affect the nail.

Splinter haemorrhages of the nail

These are thin lines of blood running along the nail bed. Causes include injury, severe anaemia, infective endocarditis (inflammation of the inner tissue of the heart) and certain diseases such as rheumatoid arthritis.

Other diseases and nails

Some diseases that can affect the shape, integrity and colour of our nails include:

• Lung disease
• Heart disease
• Kidney disease
• Liver disease
• Thyroid disease.

Congenital disorders of nails

Some nail conditions are congenital (present at birth). These include nail–patella syndrome, where the nails are improperly formed or missing.

Older age and nails

As our body ages, the growth rate of our fingernails and toenails tends to slow. The change of protein in the nail plate makes nails brittle and prone to splitting. Discolouration and thickening are also common.

Keratinocyte cancers occur when skin cells are damaged, for example, by overexposure to ultraviolet (UV) radiation from the sun. Between 95% and 99% of skin cancers in Australia are caused by exposure to the sun. The risk of skin cancer is increased for people who have:

• increased numbers of unusual moles (dysplastic naevi)
• fair skin, a tendency to burn rather than tan, freckles, light eye colour, light or red hair colour
• had a previous skin cancer
• people who are immune suppressed either as a result of medication (e.g. for solid organ transplant) or from a blood disorder or lymphoma.