Chapter 12 Management of allergy, rashes and itching
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:
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.
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:
Patients with a normal primary survey with obvious need for hospital admission
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)
History
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.
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.)
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
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.
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:
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.
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) |
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.
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:
Where indicated, appropriate home management options are discussed for each condition.