There are around 4,000 possible dermatological diagnoses, yet in primary care four conditions – acne, eczema, psoriasis and leg ulcers – account for nearly three quarters of all consultations. Other conditions encountered include viral, bacterial and fungal infections, as well as benign and malignant skin lesions.

Although impossible for pharmacists to be familiar with every diagnosis, a systematic approach can often help to narrow the diagnosis and identify a likely cause. It is necessary therefore for pharmacists to undertake a complete dermatological history when assessing patients with skin problems.

A systematic approach to questioning the patient will often help to establish the cause. In addition to the suggested questions it is worth enquiring about:

  • - Stress and anxiety – some conditions such as eczema or psoriasis can worsen during periods of stress
  • - Patients’ perception – although patients always blame detergents and new wash products, it often helps to listen to what the patient thinks might be the cause of the problem.   

Examining the patient

Once a history has been taken it is necessary to examine the rash or lesion. This should ideally be undertaken in daylight, or at least with a good light source. Important factors to consider include:

  • - Site and distribution of the problem – eg a rash in the elbow flexures and behind the knees in a child might well be eczema.
  • - Symmetry – if the skin problem has an endogenous cause, it is likely to occur on both sides of the body, eg eczema or psoriasis, whereas asymmetrical rashes, eg tinea infections such as athletes’ foot, often affect only one foot. Allergic contact dermatitis is another condition which tends to be asymmetrical.
  • - Shape and border – in psoriasis, for example, plaques are well demarcated whereas in eczema, the border is less well defined. Discoid eczema lesions are typically coin shaped. A clue to the diagnosis of fungal infections such as tinea, is that lesions have a raised border.
  • - Itch – the presence or absence of itch can aid the diagnosis. For example, eczema can be an extremely itchy condition such that if the skin does not itch, then eczema can be excluded as a diagnosis.
  • - Scale – many skin conditions give rise to surface scale and, although the presence of scale per se is not diagnostic, it can provide a clue when considered in conjunction with other features.
  • - Colour – not all skin problems are red! Lichen planus is considered to be violaceous (violet coloured) and some conditions such as pityriasis alba lead to hypo-pigmentation.
  • - Type of lesions – the nature of the lesion can aid the diagnosis. For instance, pompholyx eczema presents as papulovesicular lesions on the hands and feet (see figure) and these characteristic lesions help with the diagnosis.
  • - Time-scale – the length of time the skin problem has been present can sometimes help with the diagnosis. For instance, impetigo, infected eczema and herpes simplex can develop in a matter of 2–3 days. In contrast, tinea, eczema and even skin cancers tend to develop over a period of a few weeks to months.

The language of dermatology

As in other areas of medicine, pharmacists need to be familiar with the language of dermatology. The effect of a problem on the skin surface also involves a number of specific descriptors:

  • - Redness is described as erythema, which is caused by vasodilatation, and blanches when pressure is applied
  • - Purpura is caused by extravasation (ie blood outside the vessels) of blood and does not blanch under pressure
  • - Exudate is serum discharged from the skin, eg in eczema
  • - Crust is formed when exudate dries on the skin, as seen in impetigo
  • - Scale is a visible accumulation of skin cells (eg psoriasis) due to aggregation and an abnormality of the shedding process (normally we shed millions of invisible skin cells every day)
  • - The skin can also fissure (or crack) and this is evident in problems such as contact irritant dermatitis
  • - If the skin condition is itchy (eg in eczema) the skin will show superficial ulcerations, termed excoriations, that are a result of continual scratching
  • - Finally, the skin responds to the continued scratching by undergoing thickening, which is termed lichenification.

Conditions affecting the face

Common problems occurring on the face in children include atopic eczema, impetigo and herpes simplex. Differentiating between impetigo and herpes simplex can be difficult in the early stages (see flow chart). A clue to diagnosing atopic eczema is that other body sites, such as the elbow flexures and behind the knees, are often also affected.

Common facial problems in adults include acne, rosacea and seborrhoeic eczema. Both acne and rosacea can have inflamed papules and pustules. In rosacea, the papules and pustules are present on an erythematous background, occurring typically on the cheeks, forehead and chin. Acne can be distinguished from rosacea by the presence of comedones, which are absent in rosacea. Furthermore, although acne can and does persist into middle age, rosacea tends to first present in the second or third decade.

Seborrhoeic dermatitis is a scaly erythematous rash which affects the central area of the face, eye brows and beard area. It also causes a greasy and scaly scalp and can occur in flexural sites as well-defined, shiny erythematous lesions. Seborrhoeic eczema occurs in babies as cradle cap. The main differential is psoriasis, although seborrhoeic dermatitis does not cause scaling on extensor surfaces or affect the nails. However, some specialists maintain that seborrhoeic eczema is a milder form of psoriasis, often referred to as ‘sebopsoriasis’. Patients with seborrhoeic dermatitis often find their condition flares during the winter months or during periods of illness and stress, which is a potential clue to the diagnosis.

There are a number of possible causes of childhood rashes and it is beyond the scope of this article to discuss all of them. Many rashes in children are associated with systemic symptoms such as headache, fever or general malaise, in which case the rash is referred to as an exanthem.

Again, there are many causes of rashes in adults and some overlap with rashes in children.

There are several different skin lesions, some of which are benign and others which are malignant or have the potential to become malignant. If pharmacists are unsure patients should always be referred to the GP.

Questions to ask a patient who presents with a skin problem

Taking a history is extremely important in trying to establish the diagnosis. Asking the patient the following questions will help to establish the cause of the problem:

  • - Where did the problem start?
  • - Where has it spread to?
  • - Has the appearance changed?
  • - Does it itch?
  • - Does anyone else in the family have a similar problem?
  • - Have you or anyone in the family ever had this problem before?
  • - What is your occupation? Have you any hobbies?
  • - What medication are you currently taking?
  • - Have you used any treatment on this problem?
  • - Is there anything that seems to make the problem better or worse?
  • - In what ways does it bother you?

Dr Rod Tucker is a community pharmacist, visiting research fellow studying the role of pharmacists in the management of eczema at the Institute of Health Sciences, University of Leeds, and a project guardian for the CPPE dermatology packages