How to spot a rash: history-taking in skin conditions – part 1


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By Rod Tucker
Community pharmacist

18 Dec 2018

When advising patients on skin complaints, it’s best to get the whole story to make the most accurate diagnosis, says Rod Tucker

Key learning points

• History-taking can help narrow down a diagnosis

• There are no ‘obvious’ questions

• Certain jobs increase the likelihood of some conditions

With more than 2,000 different skin diseases, it can seem an insurmountable task to determine the cause of a patient’s rash. This difficulty is further compounded by the fact that most health professionals receive little undergraduate training in dermatology. Fortunately in primary care, it has been estimated that four conditions – acne, eczema, psoriasis and leg ulcers – account for nearly three quarters of all consultations.

Though it is virtually impossible, and unnecessary, for pharmacists to become familiar with every single dermatological diagnosis, the importance of a systematic approach to history taking should not be underestimated and will help narrow down the potential causes of a skin condition.

Before gathering information on the history of the problem, a consideration of demographic data is useful and may
have some bearing on the diagnosis.

For instance:

• Age: Infectious diseases, such as viral rashes, are more commonly seen in children, whereas malignancy is more prevalent in those with advancing age. Certain problems are also generally age specific. Acne, for example, normally affects teenagers, while rosacea is normally seen in those aged 45-60 years.

• Gender: Melasma is more common in women whereas fungal infections in the groin and feet are more prevalent in men.

• Race: Both vitiligo and post-inflammatory hyperpigmentation are usually seen in those with darker skin.

 

Information gathering

 

Firstly, never assume that the patient will provide all the necessary information. Even the most obvious questions will need to be asked. Secondly, ask about any previous history of the current problem as this might provide clues to the diagnosis. For example, a photodermatitis may be triggered every spring whereas eczema and psoriasis often reappear during the colder months. If it is a new problem, the following questions can help establish the most likely causes:

 

How long have they had it?

The timescale for a problem can help establish a possible diagnosis. For example, drug eruptions, allergic contact dermatitis and impetigo develop over a matter of days, while fungal infections and psoriasis develop more insidiously.

Any changes in lesions over time may be diagnostic. For instance, urticarial wheals from an allergic reaction will typically resolve after 24 hours without a trace whereas psoriatic plaques change over several weeks and become increasingly covered in scale.

Where did it start?

Some conditions have a typical distribution, eg psoriatic lesions characteristically develop on extensor surfaces (for instance, elbows and knees) and along the hairline, whereas eczema normally affects the flexor surfaces (ie elbow creases).

Other conditions might have started at different site to the current problem and this may also help determine the most likely cause. A tinea infection in the groin, for instance, may have started as athletes’ foot. Pityriasis rosea invariably starts with a single larger lesion (Herald patch) on the trunk and subsequently spread to affect the limbs after a few days.

Location and distribution

Ideally, it is necessary (but not always possible) to examine the whole skin since patients may not think to mention all of the areas affected. The location of a problem may help with the diagnosis as certain conditions tend to affect specific areas of the body.

 

Associated symptoms

 

Pruritus

Itch is a frequent and poorly-tolerated symptom, often waking patients at night,
and can be connected with skin excoriation (scratch marks). In conjunction with information on the distribution of the problem, the presence of pruritus is a useful diagnostic aid.

Pruritis is very commonly seen with:

• Scabies

• Atopic eczema

• Contact dermatitis

• Insect bites

• Lichen planus

Pruritis is a symptom, although much less of a problem, with:

• Psoriasis

• Tinea infections

• Pityriasis rosea

• Drug eruptions

Systemic diseases

• In the absence of any obvious skin symptoms, pruritus can be caused by
several systemic illnesses such as:

• Renal disease

• Liver failure

• Diabetes

• Hypothyroidism

Such patients should be referred to their GP for investigation.

Other symptoms might include:

• Pain: eg herpes zoster (shingles)

• Tenderness: eg inflammatory conditions such as eczema

• Bleeding: eg may be seen with malignancy

• Discharge: eg often seen with infected lesions

Systemic symptoms

Always ask patients if they have any systemic symptoms, such as pyrexia, malaise, joint pains or any evidence of swelling that could indicate an underlying malignancy or systemic disease such as systemic lupus erythematosus.

 

Who else has it?

As some conditions – including eczema and psoriasis – have a genetic basis, the presence
of these in a first-degree relative could offer important diagnostic clues. Even the presence of associated atopic diseases, such as asthma and hayfever, raises the possibility of eczema as a cause for the rash.

Alternatively, the presence of similar symptoms in other family members may indicate a contagious cause, for example, scabies or head lice.

 

What’s their occupation?

Certain jobs increase the risk of developing specific skin problems. Typically, hairdressers, mechanics, bricklayers and even gardeners will suffer from irritant hand dermatitis and allergic contact dermatitis due to exposure to solvents, cements, pesticides and even plants.

Asking about whether any work colleagues have similar symptoms is also a useful indicator of the potential cause.

 

What medicines are they taking?

A full drug history is important, including both prescribed, over-the-counter treatments and any new cosmetics. Topical antibiotics can lead to allergic contact dermatitis and systemic agents such as tetracyclines are associated with photoallergic reactions.

Ask about any recently started medicines, either when the rash started or in the preceding two to three weeks before the problem began.

 

Have they already tried using anything?

Knowledge of any actions taken before seeking advice might also help your recommendations. For instance, there is little point in suggesting an emollient if the patient has already used one in an effort to self-treat the problem.

Also, applying treatments to a skin condition might alter the course of the disease. A classic example is the use of a topical steroid on a fungal rash that will lead to tinea incognita. Initially, the topical steroid will reduce the inflammatory component of the fungal infection but over time the fungal infection becomes less scaly and more pustular.

 

What makes it worse or better?

Patients with rosacea will normally reveal how their condition is worsened by exposure to sunlight, cold wind, hot spicy foods and alcohol intake. In contrast, those with eczema, psoriasis and acne will report that skin problem is improved during the warmer, sunny weather. Conditions such as work-related allergic/irritant contact dermatitis are likely to improve during holiday periods.

 

Are they under any pressure/stress?

The presence of stress through work, family problems etc. can often lead to an exacerbation of eczema, psoriasis and acne and hence it is important to ask patients if they are currently experiencing extreme circumstances.

Finally, ask the patient about how the condition affects them and don’t be afraid to ask them what they think is the likely cause.

 

Criteria for referral – red flags

Many cases of mild-to-moderate skin problems can be managed in community pharmacies. However, it is vital to appreciate which patients require referral to their GP.

Any patients with signs of infection, ie inflammation, discharge and tenderness, should be referred. Other conditions that warrant referral include:

• Moderate to severe acne – ie acne with many papules/pustules that is widespread and affecting the chest and back

• Infected eczema

• Suspected bacterial infections

• Shingles

• Drug-induced skin reactions

• Possible skin cancers/pre-malignant lesions

• Widespread fungal nail and scalp infections

• Psoriasis (apart from emollients there are no effective OTC treatments for psoriasis)

Referral is also required where there is uncertainty about the diagnosis.

 

Rod Tucker is a community pharmacist

 

More next issue

The second part of this article will consider how to examine the skin and illustrate how a good history and examination can lead to the correct diagnosis

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