Chapter 123

### Introduction

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 contact dermatitis, malignant skin neoplasms, solar keratoses/sunburn, lacerations, warts and acne.

This chapter focuses on the common dermatoses.

### Dermatitis/eczema

The terms ‘dermatitis’ and ‘eczema’ are synonymous1 and denote an inflammatory epidermal rash, acute or chronic, characterised by vesicles (acute stage), redness, weeping, oozing, crusting, scaling and itch. Dermatitis can be divided into exogenous causes (allergic contact, primary 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 (dyshidrotic), pityriasis alba, lichen simplex chronicus and seborrhoeic.

Dermatitis is primarily due to an impairment of the barrier function of the skin, making it more susceptible to irritation by soap and other contact irritants, the weather, temperature and non-specific 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, eczema, skin sensitivities and urticaria. It is not synonymous with allergy.

An estimated 10% of the population are atopics, with allergic rhinitis being the most common manifestation.2

##### Atopic dermatitis

Features of classic atopic dermatitis:3

• itch

• usually a family history of atopy

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

• often known trigger factors (see Table 123.1) are evident

• dust mite allergy is not always obvious, especially for peri-orbital rash

• lichenification may occur with chronic atopic dermatitis

• flexures are usually involved (see FIG. 123.1)

• dryness is usually a feature

Table 123.1

Trigger factors for atopic dermatitis

Sign in to your MyAccess profile while you are actively authenticated on this site via your institution (you will be able to verify this by looking at the top right corner of the screen - if you see your institution's name, you are authenticated). Once logged in to your MyAccess profile, you will be able to access your institution's subscription for 90 days from any location. You must be logged in while authenticated at least once every 90 days to maintain this remote access.

Ok

## Subscription Options

### Murtagh Collection Full Site: One-Year Subscription

Connect to a suite of general practice resources from one of the most influential authors in the field. Learn the breadth of general practice, including up-to-date information on diagnosis and treatment, as well as key clinical skills like communication.