Management of allergy, rashes and itching

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Chapter 12 Management of allergy, rashes and itching

Mike Langran, Colville Laird

Introduction 198
Basic physiology and pathology 198
Primary survey 199
Patients with a normal primary survey with obvious need for hospital admission 199
Secondary survey (including history taking) 200
History 200
Examination 202
General examination 203
Examination of the skin 203
Investigations 203
Differential diagnosis 203
Management plan 205
Immune system mediated conditions 205
Anaphylaxis and anaphylactoid reactions 205
Allergic reactions – local 209
Urticaria (‘hives’) and angioedema 209
Idiopathic thrombocytopaenic purpura (ITP) 210
Infective conditions 211
Bacterial 211
Viral 214
Other conditions 217
Other causes of isolated itching 218
Basic symptomatic measures for the relief of itching 218
Formulating a safe and effective management plan 219

Introduction

The vast majority of skin problems that present in the community are minor in nature. Unfortunately, very occasionally, the development of seemingly innocuous symptoms such as a rash and/or itching can be the presenting symptoms of a life-threatening condition – namely anaphylaxis or meningococcal septicaemia. Whilst other clinical conditions can mimic both anaphylaxis and meningitis, especially in the early stages, there are usually clues in the presentation that help to minimise the delays in administering appropriate therapy. It is not possible in this chapter to cover all potential causes of a skin rash and/or itching. Rather, this chapter aims to focus on important conditions that require recognition, treatment and possible referral in the acute pre-hospital setting. The objectives of this chapter are listed in Box 12.1.

Box 12.1 Chapter objectives

With regard to the presentation of a rash and/or itching:

image To understand the basic physiology and pathology underlying allergic causes of rashes and itching
image To perform a primary survey of the patient and treat any immediately life-threatening problems
image To identify any patients who have a normal primary survey but have an obvious need for hospital admission
image To perform a secondary survey incorporating other body systems that may be affected by a skin rash and/or itching
image To consider a list of differential diagnoses
image Discuss treatment based on the likely diagnosis(es)
image Discuss appropriate patient follow-up
image Describe who can be safely considered for home treatment

Basic physiology and pathology

Allergic reactions are linked to the release of chemical mediators, which are released from mast cells in a process known as degranulation.1 This occurs when an allergen cross links with immunoglobulin E (IgE) bound to receptors on mast cells. These chemicals are either released immediately (immediate allergic reaction), or after a few hours (late phase response) (Table 12.1). This timing helps to guide appropriate treatment.

Table 12.1 Release of chemical mediators from mast cells

Timing of release Examples Treatment
Immediate Histamine, tryptase, hydrolases Anti-histamines (e.g. chlorpheniramine, cetirizine)
Delayed Prostaglandins, leukotrienes, cytokines Steroids (e.g. prednisolone)

Primary survey

Assess for an ABC problem in patients with itching and/or a rash (Box 12.2). The recognition of developing airway obstruction is critical, particularly in the presence of anaphylaxis. Patients may complain initially of a feeling of tightening in the throat, be unable to complete sentences or have audible airway noise (stridor or wheeze). If airway obstruction becomes complete, then prompt initiation of a surgical airway will be required.

Box 12.2 Primary survey

Arrange immediate treatment and transfer to hospital if any of the following are present:

image Signs of airway obstruction
image Respiratory rate <10 or >29
image Oxygen saturation <92% on air
image Pulse rate <50 or >120
image Systolic BP <90
image GCS <12

Patients with a normal primary survey with obvious need for hospital admission

The following conditions may present initially with a normal primary survey but immediate treatment (if appropriate) and hospital admission should be initiated:

image Suspected rash of meningococcal septicaemia
image Definite exposure to a trigger that has previously led to an anaphylactic reaction
image Self-administration of epinephrine by a patient for a suspected anaphylactic reaction
image A suspected anaphylactic reaction that has not fully developed
image Cellulitis – patient clinically toxic or affecting the peri-orbital tissues.

The history and findings on examination should help to establish whether you are faced with such a scenario. Although these patients may not have abnormal clinical signs at the time of assessment, this should not lull you into a false sense of security since they may deteriorate rapidly. In the case of suspected meningococcal septicaemia, early administration of appropriate antibiotic therapy is safe and associated with an improved prognosis.2 Whenever there is a suspicion of anaphylaxis, epinephrine for intramuscular injection should be readily available.3 If the above situations present, based on the history and examination findings as described in this chapter, then appropriate treatment should be administered and hospital admission arranged.

Secondary survey (including history taking)

Having ensured that your patient has no immediately life-threatening problems on their primary survey or the need for immediate hospital admission, you will be left with a patient for whom a careful history and examination should elucidate whether further treatment is required and whether or not the patient can be safely left at home. A history of the presenting complaint should be taken, any other information noted and an examination performed as described earlier in this series. Remember that the skin is the largest organ in the body and adequate exposure may be required to allow a thorough examination to be completed. Obviously, the degree of exposure will be dictated by the prevailing circumstances and nature of the presenting complaint(s).

History

The following will be helpful in establishing the diagnosis in someone presenting with a rash or itching. Unfortunately, there are few clinical tests that can help in the diagnostic process, which relies heavily on the use of a logical process to identify and eliminate serious problems.

Onset of symptoms

Did the symptoms come on suddenly over the course of a few minutes/hours or more gradually over the course of several days? Has there been recent injury to the area affected (especially a laceration)? Can symptoms be related to a particular event? In particular, the patient may be able to associate the symptoms with a specific trigger, e.g. consumption of a particular meal, use of a new shampoo, etc. The common potential triggers for an anaphylactic reaction are listed in Table 12.2.

Table 12.2 Potential triggers for anaphylaxis

Cause Examples
Foods Nuts and seeds, eggs, seafood, kiwi fruit, bananas
Venom/stings Bees, wasps, jellyfish, ants, snakebites
Drugs Antibiotics, aspirin/NSAIDs*, vaccines, radio contrast dye
Physical contacts Latex rubber
Other Cold temperatures, exercise

* Non-steroidal anti-inflammatory drugs (e.g. ibuprofen, diclofenac, naproxen, etc.)

PITFALL

Nuts are increasingly being used as a ‘filler’ in a wide range of foods – the patient may not therefore be aware that they have consumed nut products

Rash/swelling

If a rash is present then is it localised or generalised? What colour is the rash? Does the area of the rash itself itch or is it actually painful to touch? Does the rash change colour when pressed against the edge of a glass? If swelling is present, which part(s) of the body are affected? Pay particular heed to any swelling involving the mouth, tongue or eyes.

Associated symptoms

Of utmost importance is whether the patient feels generally well in him/herself. Does the patient have a generalised itch all over? Is there disturbance of another bodily system – e.g. gastrointestinal upset? Specific enquiry should be made about the presence of vomiting, headache, neck pain, cough and eye discomfort. The patient should be asked whether they have recently had an upper respiratory tract infection and/or tonsillitis.

Progress of symptoms

It is important to ascertain whether the symptoms have continued to worsen since their onset. Anaphylaxis and meningococcal septicaemia are progressive conditions that will steadily deteriorate with time. However, if a patient with an allergic reaction but without signs of anaphylaxis has remained stable for more than an hour they are unlikely to deteriorate further.

Previous episodes

Ask whether a similar episode has affected the patient before. Previous episodes of anaphylaxis are unlikely to be easily forgotten! Unfortunately, a history of a previous allergic reaction (mild or severe) does not predict the likelihood of an anaphylactic reaction – a reaction can still occur despite a long history of previous safe exposure.4

PITFALL

Someone who has had previous safe exposure to a potential trigger (e.g. peanuts, seafood, specific drugs, etc.) may still experience an anaphylactic reaction to it in the future

Risk factors

Exposure to certain triggers is associated with an increased incidence of allergic reactions (Table 12.2).

Past medical history/drug history

Any past history of similar events should be noted. Many drugs can be implicated in the development of allergic reactions and anaphylaxis. Aspirin accounts for about 3% of anaphylactic reactions and symptoms may occur hours after ingestion.5 Those allergic to aspirin may also be sensitive to NSAIDs, which may cause a similar reaction. A similar allergic relationship can occur with penicillins and cephalosporins. Even people who have had no previous problems with penicillins may experience an anaphylactoid reaction after taking them. Diabetics are at a higher risk of cellulitis.

Family and social history

A positive family history of similar episodes suggests hereditary angio-neurotic oedema (HANE), which is inherited as an autosomal dominant trait. Has the patient been in contact with anyone who has had similar symptoms or felt unwell? Is the patient worried about a particular diagnosis? If so, this should be excluded if possible so that the patient may be reassured.

Examination

See Chapter 2 relating to patient examination. It is always advisable to check and document the vital signs of any patient who presents with a possible allergic reaction or rash. This includes the measurement of temperature, pulse, blood pressure and respiratory rate. An elevated temperature and/or the presence of enlarged (and often painful) lymph glands in the submandibular and/or cervical regions suggests the possibility of an infective process. It is sensible to test for neck stiffness in any patient who presents with a rash and systemic upset. The patient’s neck should be passively flexed forwards towards the chest wall, a manoeuvre that should not be painful to complete. If neck flexion causes pain, then Kernig’s and Brudzinski’s signs should be tested:

image Kernig’s sign. Extend the knee with the hip flexed – positive test if hamstrings contraction occurs as a result
image Brudzinski’s sign. Flex the neck passively – test is positive if the knees and hips flex as a result.

PITFALL

Although a positive response to Kernig’s or Brudzinski’s tests is diagnostic of meningism, the absence of a positive response does not rule out meningitis

General examination

Note the patient’s overall demeanour. Do they appear well, at ease and able to converse normally or are they anxious, sweaty, confused or making abnormal noises as they breathe? If this is the case, go back and reassess their primary survey and consider whether further treatment and/or onward referral are required.

Examination of the skin

As previously mentioned, it is important to ensure adequate exposure of the skin, especially in younger children who may be less able or likely to bring the presence of a rash to your attention. In a significant proportion of patients with meningococcal septicaemia, the rash starts on the palms of the hands and/or the soles of the feet so be sure to examine these carefully. Is the rash painful to the touch? Document any swelling of the tissues, especially around the face and the eyes. Gently examine inside the mouth looking for swelling of the tongue. Note the presence of any scratch marks on the body. Note the colour associated with any rash – does the rash disappear or change colour when pressure is applied? (Ideally this should be done with the base of a clear glass.) Table 12.3 lists the common terms used to describe physical changes in the skin associated with the presence of a rash.

Table 12.3 Terms used to describe rash-induced skin changes

Terminology Description Clinical examples
Macular Non-infiltrated flat lesions which differ in colour from adjacent areas of skin Erythema, purpura
Papular Well demarcated raised lesions in the skin of varying sizes Urticarial wheals, planar warts
Vesicular Small protuberances with a central cavity containing clear liquid Chickenpox
Excoriations Very superficial wounds in the surface of the skin Scratches
Purpura Small patches of non-blanching discolouration caused by bleeding from small superficial blood vessels in the skin Petechiae – Small spots of purpura Ecchymoses – Large confluent patches of purpura Meningococcal disease Idiopathic thrombocytopaenic purpura (ITP) Henoch–Schonlein purpura (HSP)

PITFALL

Although a non-blanching purpuric rash should be considered to be indicative of meningococcal septicaemia in the pre-hospital setting, neither the absence of a rash nor the fact that a rash blanches should be considered as ruling out meningitis or septicaemia

Investigations

There are few investigations that will quickly confirm the diagnosis of a rash or itching in the acute pre-hospital setting. The diagnosis usually requires a clinical interpretation of the symptoms and signs presented.

Differential diagnosis

Table 12.4 lists the main important conditions to be distinguished in a patient presenting with a rash and/or itching. Further information is given later in this chapter specific to each condition.

Table 12.4 Conditions presenting with rash and/or itch or itch alone

Rash ± itch Itching alone
Immune system mediated
Anaphylaxis
Anaphylactoid reaction
Allergic reaction – local
Urticaria (‘hives’) and/or angioedema
Idiopathic thrombocytopaenic purpura (ITP)
Infective
a. Bacterial
Meningococcal septicaemia
Cellulitis
Impetigo
Scarlet fever
b. Viral
Varicella zoster
Primary infection (chickenpox)
Reactivation (herpes zoster or ‘shingles’)
Measles
Rubella (German measles)
Non-specific viral rash
c. Other conditions
Henoch–Schonlein purpura
Psoriasis
Eczema		 Immune system mediated
Anaphylaxis
Anaphylactoid reaction
Systemic
Systemic upset (e.g. uraemia, cholestasis, blood disorders)
Other
Senile itch
Solid tumours
HIV

Management plan

Depending on the suspected diagnosis and clinical condition of the patient, the usual management plan can be summarised as one of the following five choices:

image Group 1 – Features requiring hospital referral. Examples would be an unwell child with a suspected meningococcal rash, an anaphylactic reaction.
image Group 2 – Patients who need a disease ‘rule-out’. These are borderline cases with some features of a diagnosis but the clinical picture is not sufficiently clear to make a definite decision on management. They need further investigation and possibly further observation. Examples would be a petechial rash in a well child. These cases may need to be referred to A&E or to the appropriate inpatient team.
image Group 3 – Common features allowing diagnosis of a problem which may be treated at home. Examples would include a young man with urticaria and no features of anaphylaxis or scabies.
image Group 4 – Type of patient who may be treated by a wait-and-see approach. This group has no specific symptoms or signs that indicate serious pathology at the time of assessment. These patients may be managed at home with advice that the diagnosis is not clear but at present there are no signs of serious pathology. The patient should be advised to seek further advice if symptoms fail to settle or get worse.
image Group 5 – Social implications. Some patients may need referral, such as the very elderly or very young, due to difficulty coping at home as well as the tendency for more rapid deterioration in condition.

Where indicated, appropriate home management options are discussed for each condition.

Immune system mediated conditions

Anaphylaxis and anaphylactoid reactions

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