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The power of making a correct diagnosis is the key to all success in the treatment of skin diseases; without this faculty, the physician can never be a thorough dermatologist, and therapeutics at once cease to hold their proper position, and become empirical..

LOUIS A DUHRING (1845–1913)

Skin disorders are common. They account for 10.8% of all problems1 encountered in general practice, the most common being dermatitis/eczema, malignant skin neoplasms, solar keratoses, lacerations, warts and acne.

This chapter focuses on the common dermatoses.


Dermatitis is a non-specific inflammatory response of the skin, presenting as an erythematous rash, that is usually itchy, and sometimes scaly.2 The terms dermatitis and eczema are often used interchangeably, with eczema referring to the process that causes dermatitis.

Dermatitis can be divided into exogenous causes (allergic contact, irritant contact, photo-allergic and phototoxic) and endogenous, which implies all forms of dermatitis not directly related to external causative factors. Endogenous types are atopic, nummular (discoid), vesicular hand/foot (pompholyx) and pityriasis alba.

Dermatitis can occur as the result of dry skin, which impairs the barrier function of the skin, making it more susceptible to irritation by soap and other contact irritants, the weather, temperature and nonspecific triggers.

The meaning of atopy

The term ‘atopic’ refers to a hereditary background or tendency to develop one or more of a group of conditions, such as allergic rhinitis, asthma and eczema. It is not synonymous with allergy.

An estimated 10% of the population are atopics, with allergic rhinitis being the most common manifestation.3

Atopic dermatitis

Features of classic atopic dermatitis:2,4

  • itch

  • usually a family history of atopy

  • about 20% of children are affected, signs appearing between 3 months and 2 years

  • specific triggers (see TABLE 113.1) may be evident

  • food allergies are rarely the main cause of the condition

  • lichenification may occur with chronic atopic dermatitis

  • flexures are usually involved (see FIG. 113.1)

  • dryness is usually a feature

Table 113.1Trigger factors for atopic dermatitis
FIGURE 113.1

Atopic dermatitis in the flexures of the knees: a typical location

Criteria for diagnosis

  • Itch

  • Typical morphology and distribution

  • Dry ...

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