Skin, Hair, and Nail Disorders

Skin, Hair, and Nails

Many skin disorders can affect several or all areas of the body surface at once. Some of these disorders have a strong inherited component, but often the cause of a particular condition is not known. Not all generalized skin problems are curable – some recur intermittently throughout life – but most can be controlled effectively with treatment and self-help measures.

Most generalized skin disorders do not pose a serious threat to health, but chronic conditions, such as psoriasis and eczema, can affect the quality of life and require long-term treatment. Other disorders cause only temporary discomfort and often clear up without treatment. Some conditions are the result of an allergy to substances such as drugs and disappear after the cause has been identified and eliminated.

The articles in this section discuss disorders that cause widespread rashes, itching, flaking, or blistering. Disorders that affect particular areas of skin are discussed elsewhere (see Localized skin conditions, and Skin infections and infestations). Disorders that affect the skin of children are discussed in a separate section (see Infancy and childhood). Rashes that affect the skin as part of an infectious disease, such as rubella or measles, are also found elsewhere (see Infections and infestations).

Key anatomy

For further information on the structure and function of the skin.



Atopic Eczema

Contact Dermatitis

Seborrhoeic Dermatitis

Blistering Diseases

Lichen Planus

Erythema Multiforme

Pityriasis Rosea


Drug-induced Rashes



Localized skin conditions are those that affect the skin on only one part of the body or on a small area. Many of these conditions are related to specific sites because they are associated with structures such as particular glands in the skin, or because of the localized effects of factors such as pressure or exposure to sunlight.

Acne and rosacea, two types of rash, are described first in this section. The next articles cover conditions that are associated with sweat glands or with under- or overproduction of melanin, the pigment that gives skin its colour.

Skin cancers, which are increasingly common, are given extensive coverage. It is important to be able to recognize the signs of cancerous changes in the skin, and the various types of skin cancer are described in detail to help you to identify them. Subsequent articles describe several noncancerous forms of swelling and growth. The final articles cover localized skin defects caused by factors such as friction or poor blood circulation.

Localized disorders due to infection are described in another section (see Skin infections and infestations). Skin problems specific to babies are discussed elsewhere in the guide (see Infancy and childhood), as are minor injuries such as sunburn (see Minor skin injuries).

Key anatomy

For further information on the structure and function of the skin.



Prickly Heat





Skin Cancer

Basal Cell Carcinoma

Squamous Cell Carcinoma

Malignant Melanoma

Kaposi’s Sarcoma

Solar Keratosis

Discoid Lupus Erythematosus

Erythema Nodosum

Skin Tag

Seborrhoeic Keratosis

Sebaceous Cyst

Calluses and Corns


Stretch Marks


Leg Ulcer

Pressure Sores

The skin surface provides the body with protection from the environment and from infection, but the skin itself may become infected by bacteria, viruses, or fungi. Some of these organisms live naturally on the body and do not normally cause disease unless they breach the barrier of the skin’s surface. Infestation of the skin by parasites, such as mites, may also occur.

Infectious organisms can enter the skin in various ways. Natural openings, such as a hair follicle or sweat gland, or broken skin at the site of an insect bite or a cut may provide a gateway for bacteria. Warm and moist areas, such as the skin between the toes, are more susceptible to fungal infections. Some common viral skin infections, such as warts, can be spread from one part of the body surface to another or may be passed from one person to another by direct skin contact.

In this section, bacterial skin infections are described first, followed by fungal and viral infections. The final article covers infestation by the scabies mite.

Diseases such as measles and rubella, in which a skin rash occurs due to an infection that also affects many other areas of the body, are covered elsewhere (see Infections and infestations). The two common skin infestations head lice and pubic lice are also described in other sections of the guide.

Key anatomy

For further information on the structure and function of the skin.






Athlete’s Foot

Pityriasis Versicolor

Cold Sore


Molluscum Contagiosum


The skin is remarkably resistant to the wear and tear of everyday life, but from time to time it may be affected by minor injury. Hands and feet are especially vulnerable to cuts, scrapes, and blisters. In a healthy person, superficial skin injuries normally heal rapidly, and most do not need attention from a doctor.

The most common types of skin injury are minor cuts and scrapes, in which the outer layer of the skin is broken. These types of wound are usually trivial, although they may be painful and there is a risk of infection entering the damaged site.

Sunburn is another common minor skin injury but one that is usually avoidable. Damage to the skin caused by overexposure to sunlight may not always appear serious, but, in the long term, sunburn increases the risk of potentially dangerous skin cancers. Friction and burns can cause damage to tissues beneath the surface of the skin, which often remains unbroken. Leaking blood and other fluids from this damage are trapped under the skin and appear as bruises or blisters. Although minor burns and scalds can be painful, most heal well within a few days if treated promptly.

Simple self-help measures are often the only treatment needed for minor skin injuries. Burns, which can be serious, are discussed elsewhere in the guide.

Key anatomy

For further information on the structure and function of the skin.

Cuts and Scrapes

Needlestick Injury




Hair and nails, like the outer layers of skin, are made of dead cells that grow from a living base. The dead parts that show above the skin’s surface can be cut or damaged without causing pain, but damage to the living roots is painful. The condition of the hair and nails often reflects general health. Changes in the nails, in particular, may indicate an underlying disease.

Most hair and nail disorders are not a health threat but may be unsightly and cause embarrassment. However, some are caused by serious health problems. For example, excessive growth of body hair may be due to a hormonal imbalance, and spoon-shaped nails suggest iron deficiency. In these cases, treating the underlying disorder often improves the condition. Hair disorders may be due to factors such as drug treatments and localized skin diseases. Many nail abnormalities are usually due to minor injury or infection but they can be difficult to treat because topical preparations do not penetrate the nail. A damaged nail will not appear normal until it grows out, so the condition of the nails is sometimes an indication of past rather than present health.

This section begins by describing several disorders that affect scalp or body hair. The remaining articles describe abnormalities of the nails and the skin that surrounds them. Some common scalp problems are discussed elsewhere, including head lice and seborrhoeic dermatitis.

Key anatomy

For more information on the structure and function of hair and nails, see Skin and Hair.

Hair structure

Nail structure



Male-pattern Baldness

Excessive Hair

Pilonidal Sinus

Nail Abnormalities


Ingrown Toenail

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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