When faced with a patient with a red lower limb, there is a tendency for some healthcare professionals to assume that this is cellulitis and erysipelas. However, this may be a misdiagnosis, as other chronic conditions, such as acute venous insufficiency, lymphoedema, non-specific oedema, contact dermatitis, or cardiac failure, have similar signs and symptoms (Santer et al, 2018) (Table 1). It is essential to form a differential diagnosis to ensure that correct treatment is implemented to prevent a potentially life-threatening condition developing, such as sepsis or necrotising fasciitis.  
 
Table 1. Differentiating between the causes of red lower limbs (adapted from Cranendonk et al, 2017) 
Conditions Sign and symptoms  
Allergic contact dermatitis   Area of erythema is confined to the contact area of allergen — can be caused by some moisturisers and skin preparations, for example, parabens, biocides, rubber and commonly colophony, which is an adhesive found in plasters and bandages 
Erysipelas Bacterial infection in the superficial layers of the skin. Usually caused by a breach in the skin. Margins of erythema are well demarcated, and blisters may occur. Treated with penicillin-based antibiotics 
Lipodermatosclerosis  Chronic inflammation and fibrosis of the dermis and subcutaneous tissues. Haemosiderin deposition or staining is present and is a key clinical sign of venous disease. Acute and chronic but can mimic cellulitis in the acute phase. Usually bilateral due to venous insufficiency and unlikely to be cellulitis if bilateral. Can be accompanied by varicose veins and oedema. Champagne bottle-shaped legs together with red/brown staining  
Gravitational (stasis, venous) eczema  Normally present in venous insufficiency and presents as a patchy eczematous condition of the lower limbs. Slow onset and there may be evidence of hyperpigmentation present, red, itchy scaley skin with blisters. Very superficial skin loss, but can become infected and develop into ulcers if not managed. May present in combination with lipodermatosclerosis 
Cellulitis   Inflammation within the deeper levels of the skin. May be caused by trauma or an injury as a result of streptococci, staphylococci or other organisms. Treatment is elevation, may require hospitalisation and intravenous (IV) antibiotics. The subcutaneous tissues are involved, and the area is red and swollen, although the margins are not as demarcated as erysipelas 

WHAT IS THE DIFFERENCE BETWEEN CELLULITIS AND ERYSIPELAS? 


Cellulitis is a deep, soft tissue infection, caused by gram-negative and -positive bacteria, haemolytic streptococci, staphylococci, aerobic or anaerobic gram-negative bacteria (Beldon and Burton, 2005). Microorganisms invade the host’s immune system, generally through a breach in the skin and, once established, they multiply rapidly and the patient may initially display a superficial infection of the dermal tissues — erysipelas — causing areas of painful blistering (Beldon and Burton, 2005). 

Cellulitis generally has an acute onset and patients exhibit generalised symptoms, such as fever, rigors, nausea and vomiting (Cranendonk et al, 2017). Unfortunately, some patients develop sepsis, gangrene or necrotising fasciitis, however the majority are not severely ill and recover uneventfully (Eriksson, 1996). Between 25 and 46% of people admitted to hospital may have recurrent episodes of cellulitis (Cox, 1998; Jorup-Rönström and Britton, 1987; Pavlotsky et al, 2004).  

Erysipelas is an acute infection which develops in the superficial skin layers and is characterised initially by malaise, shivering and a fever (Weller et al, 2015). Later, the affected areas become red with a well-defined margin and blisters may develop on the red plaques. Erysipelas commonly results from a split in the skin, such as between the toes or the earlobes, and toe web intertrigo and lymphoedema are risk factors. Unfortunately, erysipelas recurs in up to 20% of patients and frequent bouts can predispose patients to persistent lymphoedema (Weller et al, 2015). Left untreated, this can develop into a serious condition (i.e. cellulitis), depending on the location. However, as it is primarily caused by streptococci, it responds rapidly with systemic penicillin, often  
given intravenously.  

Although, in theory, erysipelas tends to affect the superficial skin tissues and cellulitis the deeper, this is not always the case, meaning it can be impossible to distinguish between the two (Kilburn et al, 2010). Cellulitis and erysipelas rarely occur simultaneously in both legs and if the redness is bilateral, it is more likely to be as a result of another condition, such as contact dermatitis or varicose eczema. 

Historically, erysipelas was distinguished from cellulitis using wound cultures, as it was assumed that streptococcal infection of the superficial dermis was the causative bacteria, whereas staphylococcal infection was the causative bacteria in cellulitis (Cranendonk et al, 2017). Studies have found that this is no longer the case, and both types of bacteria have been isolated in cases of both erysipelas and cellulitis (Cranendonk et al, 2017). The signs and symptoms of both conditions are very similar, and it is difficult to differentiate between them clinically. As a result, treatment and management of both are grouped together as soft tissue infections (National Institute for Health and Care Excellence  
[NICE], 2019). 

CAUSES AND RISK FACTORS FOR CELLULITIS AND ERYSIPELAS 


Cases of cellulitis and erysipelas are frequently associated with a history of trauma, such as abrasions, insect bites or lacerations (El-Daher and Magnussen, 1996). However, conditions such as lymphoedema (Figure 1), obesity and venous leg ulceration, increase the risk of erysipelas and cellulitis (Beldon and Burton, 2005; Weller et al, 2015).  

Lymphoedema increases the risk as impaired lymphatic drainage provides a static pool of protein-rich lymph, which is an excellent medium for bacterial growth (Beldon and Burton, 2005). 

There are multiple physical barriers and active protective mechanisms which fend off invasion of bacteria in the skin (Cranendonk et al, 2017). Intact, well perfused skin will prevent infection, however, there are risk factors, such as old age, diabetes and obesity which may affect the immunity, circulation and integrity of the skin and pose a relatively high risk of cellulitis. These three risk factors are often present in patients admitted to hospital with cellulitis. However, Cranendonk et al (2017) have suggested that a previous history of cellulitis is the biggest  risk factor.  

Figure 1. Cellulitis in a patient with lymphoedema.
Ageing skin is associated with atrophy, often combined with poor circulation, a less efficient immune system, together with comorbidities such as diabetes or congestive cardiac failure (Cranendonk et al, 2017). Furthermore, if the patient is malnourished, there may be impaired wound healing, decreased skin elasticity and integrity (Kish et al, 2010).  

Lipsky et al (2010) found that hospital admission rates for cellulitis are higher in patients with diabetes, often as a result of diabetic foot-associated problems, although more than a quarter of patients with diabetes admitted to hospital with cellulitis had developed this on non-foot locations (Lipsky et al, 2010).  

In patients who are morbidly obese, the skin is more susceptible to damage and may also take longer to repair (Yosipovitch et al, 2007). Indeed, it has been suggested that obesity causes changes in skin barrier function, the lymph system, collagen structure and function, and wound healing. The evidence also suggests that the vascular and macro and microcirculation may be impaired in obese patients (Huttunen and Syrjanen, 2013).  

In addition, adipose tissue contains adipokine, which impairs the inflammatory response and obese patients tend to have dry skin, and impaired skin barrier and lymphatic flow (Cheong et al 2019), all of which increase the risk of  skin infections.  

Seasonal variations have also been observed, with streptococcal skin infections occurring more frequently in the winter months  in cold climates and higher erysipelas rates in the summer in warmer countries (Pereira de Godoy et al, 2010). 

DIAGNOSING CELLULITIS AND ERYSIPELAS 

 
The classic clinical signs of cellulitis and erysipelas are: 
  • Erythema 
  • Oedema 
  • Warmth 
  • Tenderness (Atzori et al, 2013). 
However, these are relatively non-specific and can vary in severity. As a result, Cranendonk et al (2017) suggest that redness does not necessarily indicate cellulitis and discuss several studies which revealed that 31% of patients hospitalised in the Netherlands with suspected cellulitis were misdiagnosed (Levell et al, 2011; Weng et al, 2017). Furthermore, they found that when clinicians referred patients to dermatologists due to an uncertain diagnosis of cellulitis, 74% of patients were found not to have the condition (Strazzula et al, 2015).  
 
Kilburn et al (2010) conducted a Cochrane review on interventions for cellulitis and erysipelas and, for the purpose of the review, grouped cellulitis and erysipelas together as one condition, as the literature did not distinguish between the two. They found that microbiological studies, using classic blood cultures and swabs from skin lesions, only proved positive in one quarter of patients admitted to hospital. More advanced testing methods detected beta haemolytic streptococci (usually group A or G) as the most prominent bacteria, accounting for almost 80% of organisms isolated (Kilburn et al, 2010). They concluded that Staphylococcus aureus probably did not cause erysipelas, but may sometimes cause cellulitis (Eriksson, 1996). Enterococci was occasionally isolated in leg ulcers in combination with gram-negative bacteria and/or S. aureus (Eriksson, 1996).  
 
 

TREATMENT FOR CELLULITIS OR ERYSIPELAS  


National Institute for Health and Care Excellence (NICE, 2019) guidance on managing cellulitis and erysipelas recommends excluding other causes of skin redness, such as an inflammatory reaction to an insect bite, or other conditions, such as chronic venous insufficiency, eczema or oedema. Furthermore, it recommends taking a microbiological swab only if the skin is broken and there is a penetrating injury, exposure to water-borne organisms, or if the infection was acquired outside the United Kingdom. Figures 2–5 show contact dermatitis, venous eczema, erysipelas and cellulitis. 



It is recommended to draw around the extent of the redness with a single-use marker pen to monitor how it progresses before starting antibiotic therapy, but remember that the redness may be difficult to visualise in darker skin tones (NICE, 2019). People with cellulitis or erysipelas should then be offered antibiotics. However, healthcare professionals need to consider the site of the infection, severity of symptoms, risk of uncommon pathogens, for example from a penetrating injury, microbiological swab results and the patient’s meticillin-resistant Staphylococcus aureus (MRSA) status if known before prescribing  
(NICE, 2019).  

NICE guidance also recommends use of oral antibiotics as first-line treatment if the cellulitis and erysipelas are not severe and, in the case of intravenous (IV) antibiotics, to review the patient’s condition within 48 hours and revert to oral administration if there is evidence of improvement. NICE (2019) gives an extensive list of suitable antibiotics and practitioners are advised to consult their local trust formulary for guidance on which is the preferred type.  

If symptoms worsen and the patient becomes systemically unwell, with increased pain out of proportion to the infection, or there is no sign of improvement after two to three days, it is recommended that healthcare professionals consider if there is another serious underlying condition, such as osteomyelitis, septic arthritis, necrotising fasciitis or sepsis (NICE, 2019). If a microbiological swab has not been taken, this should be done now, and the patient should be changed to a narrow spectrum antibiotic (NICE, 2019). 

Santer et al (2018) note, however, that although cellulitis is usually treated with a one-week course of antibiotics, such as flucloxacillin, dependent on severity, comorbidity and site of infection, in many cases it does not resolve after one week and patients often receive repeated doses of antibiotics. They suggest that this may be unnecessary as the persisting redness can be due to inflammation, rather than active infection.  

Santer et al (2020) also suggest that there is little evidence to guide the route of administration and that oral antibiotics appear to be just as effective as the IV route. As a result, they question the NICE Clinical Knowledge Summary guidelines, which recommend that patients with cellulitis, who are systemically unwell or who have diabetes, obesity, peripheral vascular disease, or chronic venous insufficiency, should be referred for either admission or IV antibiotics. Santer et al (2020) conclude that this advice is based on opinion rather than clinical evidence and that the majority of patients, with the exception of the systemically unwell, could be managed  
at home.  

This lack of guidance on prescribing antibiotics in cellulitis and erysipelas has also been highlighted by Bishop et al (2021) and Kilburn et al (2010). Beldon and Burton (2005) have produced a helpful algorithm for the management of limb cellulitis in primary and secondary care. 

NICE (2019) does not recommend the routine use of prophylactic antibiotics to prevent future infections. However, the British Lymphology Society (BLS) guidelines recommend that patients with lymphoedema, who have had an attack of cellulitis, carry a two-week supply of antibiotics with them, particularly when away from home for any length of time, e.g. on holiday. Amoxicillin 500mg tds is recommended or, for those allergic to penicillin, erythromycin 500mg qds or clarithromycin 500mg bd (BLS, 2016). 

Tissue viability management of ‘red legs’ 


As said, clinical signs of erysipelas/cellulitis can mimic other conditions, such as allergic contact dermatitis which is caused by exposure to an allergen or irritant substance that has damaged the normal barrier function of the skin (Beldon and Burton, 2005; Figure 6).  
 

Clinically, these conditions will produce inflammation, oedema, pain, exudate, and blistering (English, 1997). In the case of venous disease, there may well be evidence of excessive keratin formation and thickening of the epidermis (Beldon and Burton, 2005). Patients with chronic venous leg ulcers may develop contact dermatitis as a result of long-term use of wound management products and the use of latex gloves (Tavadia et al, 2003). It is for this reason that latex gloves should  be avoided. 

If the patient has ‘wet’ cellulitis, venous eczema or contact dermatitis, the legs should be washed daily with a mild soap substitute, followed by moisturising with a bland emollient. Generic 50/50 liquid paraffin in soft white paraffin is the treatment of choice (Weller et al, 2015). Thirty minutes after applying an emollient, a potent steroid cream should be sparingly applied to the affected areas for a maximum of two weeks. If this does not resolve the skin’s condition, a reduced strength steroid cream can be used (Weller et al, 2015). 

Exudate management may require the use of alginates or Hydrofibers as primary dressings, with absorbent secondary dressings, for example, Zetuvit® (Hartmann) or Exu-dry® (Smith and Nephew). However, in the initial phase, dressings may need frequent changing to prevent maceration (Beldon and Burton, 2005). Alternatively, superabsorbent dressings, such as Cutimed Sorbion Sachet Extra® (Essity) or Eclypse® (Advancis Medical), can be used. Healthcare professionals should consult their local trust’s dressing formulary for preferred choices. 

If the patient is able to self-care, it may be more cost-effective to use a non-adherent contact layer, such as Adaptic™ (3M + KCI), Atrauman® (Hartmann) or Mepitel® (Mölnlycke), which can stay in place for several days, with the patient changing the outer dressing  as required.  

Potassium permanganate soaks are sometimes used as a weak antiseptic, however the effectiveness of these is debatable and there is no robust research evidence currently available to support their use. If using potassium permanganate, care must be taken to obtain the correct dilution of 1:10,000, as using a stronger solution may cause skin irritation (Beldon and Burton, 2005).

Pain relief and elevation 


Two main components of treatment for acute erysipelas/cellulitis and venous eczema are elevation and pain relief.  

Cellulitis is a painful condition and without adequate pain relief, the patient will not tolerate elevation. Elevation will reduce oedema and patients should be encouraged to rest for periods during the day, with the affected limb raised on pillows if necessary (Beldon and Burton, 2005). It may also be possible to raise the foot of the bed.  

However patients, particularly the elderly, still need to mobilise to use the toilet and prevent problems such as deep vein thrombosis (DVT) and a reduction in mobility (Beldon and Burton, 2005). Foot exercises, such as dorsiflexion, will also help to reduce oedema by using the calf muscle pump (Hofman, 1998). As the oedema subsides, patients should be warned that the skin may become wrinkled and slough away in sheets. Frequent application of emollients can help to prevent this from occurring.  

Compression therapy 


Atkin (2017) suggested that there is insufficient robust research evidence to support the use of compression to treat varicose eczema. However, compression will reduce oedema by improving lymphatic uptake by lessening the amount of lymph fluid in the legs. Application of compression stockings will also treat venous hypertension and therefore may slow down the development of skin changes responsible for venous eczema. Accordingly, NICE (2020) advises offering the use of compression hosiery in the long-term management of varicose eczema, where arterial insufficiency has been excluded.  

In patients with limb cellulitis secondary to venous ulceration, it is commonly thought that compression therapy should be discontinued, as it is contraindicated in acute infection (Atkin, 2017). This is not the case  and the decision to continue with compression should be based on individual patients and their ability to tolerate compression if the cellulitis is painful (Atkin, 2017; Cranendonk et al, 2017). If pain is well-controlled, there is no reason why compression should not be applied. If the patient is unable to tolerate compression, they should be encouraged to elevate their limb during the day.

CONCLUSION 


Cellulitis and erysipelas of the lower limbs are common conditions which are frequently misdiagnosed as they may mimic other conditions, such as varicose eczema or contact dermatitis. As a result, patients may be hospitalised unnecessarily, while their care could have been managed successfully in the community.  

Ensuring that only patients who require hospitalisation are admitted will reduce the number of hospital stays and free up beds for those that really need admission. Furthermore, being managed at home may be more convenient for the patient and their family. 

This article has discussed the most common conditions that cause ‘red legs’, the differences between cellulitis and erysipelas to enable healthcare professionals to distinguish between them, together with an outline of treatment and nursing management. 

 

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