Fungal skin infections

Fungal skin infections are a worldwide problem and carry a substantial burden in terms of therapeutic cost and impact on healthcare resources (Urban et al, 2021). They can affect any age and vary widely in severity and treatment duration, as well as posing a challenge in terms of educating the public and promoting prevention wherever possible. This article will look at common fungal skin infections, their treatment and management and give nurses and non-medical prescribers more confidence in advising and treating patients affected by one or more of the diseases discussed. Common fungal skin infections include:

• Ringworm (tinea corporis)
• Groin infection (tinea cruris)
• Athlete's foot (tinea pedis)
• Fungal infection of the skin folds (intertrigo)
• Fungal infection of the beard (tinea barbae)
• Fungal infection of the scalp (tina capitis)
• Fungal infection of the nails (onychomycosis, tinea unguium).

Pathophysiology

Fungal infections caused by dermatophytes, a group of fungi that invade and grow in dead keratin, causing infection that is normally confined to dead layers of skin. Because dermatophytes require keratin for growth, they are restricted to hair, nails and superficial skin layers and would not normally infect mucosal surfaces (Hainer, 2003). Failure of the skin's normal protective mechanisms make infection possible and, once established, can be transmitted from person to person. Some types are more frequently seen than others, with tinea pedis being most common in adults and tinea capitis the most likely diagnosis in children (Tidy, 2021a). The most prevalent organisms are (Tidy, 2021a):

• Trichophytons rubrum: responsible for approximately 90% of all fungal infections (National Institute for Health and Care Excellence [NICE], 2018a) and a very common cause of onychomycosis and athletes' foot (Oakley, 2003a; Knott, 2015a)
• Trichophytons tonsurans: frequent cause of tinea corporis (Dermnet, 2003a)
• Trichophytons interdigitale: cause of athlete's foot (Oakley, 2003a)
• Trichophytons mentagrophytes: common cause of tinea barbae (Schwartz, 2021)
• Microsporum canis: common cause of tinea capitis (Knott, 2015a)
• Epidermophyton floccosum: common cause of tinea cruris (Dermnet, 2003b).

Risk factors

Although fungal skin infections can affect anyone, a number of risk factors have been identified, making certain individuals more susceptible. These have been identified as: living in hot humid climates or working in high temperatures, obesity, tight fitting clothing, or excessive sweating (hyperhidrosis) (NICE, 2018b). Immunocompromised patients are also more susceptible and may suffer a more severe disease, which, in some, will be resistant to treatment (NICE, 2018b). Avoidance of spread and prevention wherever possible is advised and preventative measures to achieve this are shown in Table 1.

Tinea corporis

Tinea corporis is commonly known as ringworm, its name reflecting the ring-like appearance of the typical skin lesions. It presents with a solitary patch of reddened skin, which appears as a circular lesion with a raised scaly edge and a paler centre. The condition can occur in both males and females and affects any age group but is commonest in pre-adolescents (Shukla, 2020). Spread occurs from person to person or from contact with items that have been touched by an infected person (such as towels, bed linen). Domestic pets, such as cats, dogs, and guinea pigs can also transmit ringworm to humans and are a common cause of infection in children (Starr, 2018a).

Diagnosis

Diagnosis is made on clinical examination and, in most cases, no specific testing is needed, but skin scrapings can be sent to the laboratory if the diagnosis is in doubt.

Differential diagnosis

Tinea corporis can sometimes be confused with other skin rashes. Some of these include (Shukla, 2020):

• Erythema multiforme: caused by infection or certain medications. Usually mild and self-limiting, resolving over a few weeks
• Impetigo: common in children but can occur at any age. Highly infectious but rarely serious
• Atopic dermatitis: Can occur in small patches or be more widespread
• Nummular dermatitis (discoid eczema): occurs in wet or dry forms and is treated as for atopic eczema but antibiotics may be needed if secondary infection occurs
• Pityriasis rosea: usually starts as a small area (herald patch) then becomes more widespread but resolves without treatment, usually within 12 weeks
• Plaque psoriasis: presents as circular lesions with a scaly appearance.

Complications

Recurrence can occur if the treatment is stopped too soon, and can also spread to other sites on the body. Disseminated infection is more likely to occur in the immunocompromised patient (eg those with HIV or AIDS (Bell, 2020). Secondary bacterial infection can also occur and is more common in children who also have atopic dermatitis (Bell, 2020).

Treatment and management

Antifungal creams are available over the counter and there are several products available. However, there is no evidence that one particular product is better than any other of those available (Starr, 2018a). Options available are shown in Table 2 and a guide to estimating how much cream to apply is shown for adults and children in Table 3 and 4. If inflammation and soreness are a problem, an antifungal cream containing hydrocortisone (Daktacort Hydrocortisone Cream [HC] or Canesten HC) may be prescribed to use for a short time before switching to the antifungal cream alone (Stewart, 2020) (Table 2).

Adverse effects

Some patients may experience erythema, hypersensitivity reactions, irritation or mild burning sensation with use of antifungal creams (NICE, 2018b).

Oral treatment

If the infection is extensive or severe, oral treatment may be needed. NICE guidelines recommend terbinafine (250 mg once daily for 4 weeks) as first line, or itraconazole (100 mg daily for 15 days or 200 mg daily for 7 days), or griseofulvin (500 mg daily for at least 4 weeks or 100mg daily if infection is severe) or if terbinafine is contraindicated or not tolerated (NICE, 2018b). Griseofulvin is licensed for use in children and should be prescribed as follows (NICE, 2018b):

• Children 1–11 years of age: 10 mg/kg daily (maximum dose 500 mg) increased to 20 mg/kg in severe infections, with dose reduction when response is achieved
• Children 12–17 years of age: 500 mg daily, increased to 1mg/kg in severe infections with dose reduction when response is achieved.

Table 5 shows information relating to adverse effects, and drug interactions of oral antifungal agents.

Prescribing tips

Harding (2015) detailed some helpful tips for when prescribing for fungal skin infections.:

• Terbinafine should be used with caution in patients with liver or kidney disease, autoimmune disease, pregnancy or breastfeeding. Liver function should be checked prior to commencing and then every 4–6 weeks during treatment
• Griseofulvin enhances the toxic effects of alcohol and can affect the ability to perform skilled tasks such as driving. The drug should be avoided in pregnancy and any patient with impaired liver function, and is strictly contraindicated in those with severe liver disease, acute porphyria and systemic lupus erythematosus.

Tinea cruris

Tinea cruris is the name given to fungal infection of the groin. It is also known as jock itch and is more commonly seen in adult males (Dermnet, 2003). The rash has a similar appearance to ringworm and is seen as red, sore, scaly, itchy skin in the groin area. Both sides are usually affected and the rash often spreads a short way down the inside of both thighs. Adults are affected by tinea cruris much more commonly than are children; however, the prevalence of several risk factors for the condition among adolescents, such as obesity and diabetes mellitus, is leading to a rapidly increasing incidence among this age group (Wiederkehr, 2020).

Diagnosis

Diagnosis for tinea cruris is the same as for tinea corporis.

Differential diagnosis

The appearance of the rash can look similar to tinea corporis, plaque psoriasis and dermatitis (Wiederkehr, 2020)

Complications

Treatment is usually highly effective and complications are rare, but secondary bacterial infection and recurrence are the most common complications (Tidy, 2021b).

Treatment and management

Table 2 shows treatment options. If an antifungal cream containing a steroid is prescribed, a faster relief of itching is achieved, however corticosteroid creams alone are not recommended (Dermnet, 2003). If oral treatment is needed for more severe infections, the options are the same as for tinea corporis.

Prescribing tips

It is recommended that the cream is applied to the surrounding 4–6 cm of normal skin, as well as to the rash itself (Starr, 2018b). For more severe infections, oral treatment may be needed.

Tinea pedis

Tinea pedis is thought to be the world's most common fungal infection, with estimates suggesting that proximately 70% of the population will be affected at some time in their lives. (Robbins, 2020). Prevalence is reported to increase with age, with males more frequently affected than females (Robbins, 2020). The skin between the toes, is the most common site for symptoms to develop, but the disease can spread to the sole, sides, and dorsum of the involved foot (Ely et al, 2014). There can be erythema with skin between the toes having a moist appearance, and there can also be painful vesicles. The condition can be chronic, characterised by scaling, peeling, and erythema between the toes (Ely et al, 2014).

Diagnosis

Diagnosis is usually based on clinical examination and does not require further investigation.

Differential diagnosis

The condition can sometimes be mistaken for erythema multiforme, dermatitis, psoriasis or a candida infection of the skin (Robbins, 2020).

Complications

As with other tinea infections, secondary bacterial infection can occur and are more commonly seen in immunocompromised patients. Scratching can lead to the infection spreading to the hands, while cellulitis of the lower leg can also occur as result of impairment of the skin barrier, creating a portal of entry for bacteria (NICE, 2018c).

Treatment and management

Treatment with topical agents (Table 2) is usually sufficient, unless the condition is resistant or more severe, when oral agents may be needed (see tinea corporis).

Prescribing tips

Antifungal preparations containing hydrocortisone (eg Daktacort HC or Canesten HC) should be avoided, as although they will reduce the itching, they can promote spread of the fungus worsening the condition (Starr, 2018a).

Intertrigo

This is an inflammatory skin rash that occurs in the skin folds and can affect one site of the body or several sites at the same time. It is particularly common in obese people, where there is skin-to-skin contact at sites such as the groin, axilla, below the breasts, under a protruding abdomen or in the folds of the neck. These moist warm areas of the body provide an ideal breeding ground for infection, which may be fungal or have a combination of bacterial and fungal elements. Intertrigo can be acute (recent onset), relapsing (recurrent), or chronic (present for more than six weeks) (Oakley, 2015).

Diagnosis

Diagnosis is usually made on the site and appearance of the rash and does not require additional investigations.

Differential diagnosis

There are a number of conditions that can be considered but the most common likely differential diagnoses are tinea cruris, psoriasis, erythrasma, and, less commonly, dermatitis (Aaron, 2020).

Complications

Because intertrigo commonly occurs where there is skin-to-skin contact in warm moist areas, the risk of secondary bacterial infections is high. A variety of fungi may also exacerbate intertrigo, including yeasts and dermatophytes, and candida is the fungus most commonly associated with this condition (Janniger and Schwartz, 2005).

Treatment and management

Daktacort HC can be used for 7 days but if not effective, oral antifungals may be needed (see under tinea corporis). If bacterial infection is suspected, oral antibiotics may be needed: flucloxacillin or erythromycin, or clarithromycin if allergic to penicillin at recommended doses.

Prescribing tip

Daktacort HC contains miconazole, which treats the fungal element but also incorporates hydrocortisone to reduce inflammation. If inflammation is severe, short-term use of trimovate (containing steroid, antifungal and antibiotic) can be used (Primary Care Dermatology Society, 2018a).

Tinea barbae

Fungal infections can occasionally develop on the moustache and beard areas of the face. The condition often presents with marked inflammation and pustules, exudation and crusting and any hairs come away easily (Primary Care Dermatology Society, 2021b). Several enzymes, including keratinases, are released by dermatophytes, which help them invade the epidermis, producing an inflammatory response once hair and hair follicles have been invaded by the fungi (Schwartz, 2020).

Diagnosis

If the diagnosis is in doubt infected hairs and skin scrapings can be sent to the laboratory to confirm the diagnosis.

Differential diagnosis

The condition can be difficult to diagnose as the appearance mimics that of other skin conditions and be confused with bacterial infection, acne and folliculitis (Primary care Dermatology Society, 2021).

Complications

With treatment the condition usually resolves but if untreated there may be scarring and alopecia (Schwartz, 2020)

Treatment and management

For very mild cases, topical treatment may be sufficient but more commonly oral treatment is needed (fluconazole, itraconazole or terbinafine as for Tinea corporis).

Prescribing tips

It is recommended that oral antifungal treatment is continued for several weeks, often six weeks or more (Kerkar, 2021)

Tinea capitis

Tinea capitis is also known as ringworm of the scalp, and arises as a result of tinea infection of the skin, particularly the skin surrounding hair follicles. There are several dermatophytes that can be potentially responsible, but in the UK, trichophyton tonsurans and trichophyton violaceum account for 90% of scalp infections (NICE, 2018c). The condition can affect any age but is most commonly seen in children under the age of 10 years, and is common among African Caribbean children living in urban areas (Fuller et al, 2014; NICE, 2018c). Additional risk factors identified include overcrowded environments (households and schools), hairdressing salons (shared combs) (Knott 2015a), and, when the condition does affect adults, is far more common among the immunocompromised (Dermnet, 2003a).

Diagnosis

The appearance of the infection is highly variable, making diagnosis sometimes challenging. The appearance of the scalp is influenced by the causative organism, but common features are patchy hair loss, with varying degrees of erythema and scaling of the scalp (Fuller et al, 2014).

Differential diagnosis

The are a number of possible alternative diagnoses, which include (NICE, 2018c):

• Scalp psoriasis
• Atopic eczema
• Seborrheic dermatitis
• Alopecia areata
• Folliculitis
• Discoid lupus erythematosus
• Lichen planus.

Complications

The condition can lead to hair loss, which can be severe in some patients.

Treatment and management

Once the diagnosis has been confirmed, treatment can be commenced, but is influenced by the causative fungi (Table 6).

Prescribing tips

Guidelines advise children do not need to stay away from school once treatment has commenced (Knott, 2015a). Griseofulvin is no longer available in liquid form so will need to be administered in crushed tablet form.

Onychomycosis

A fungal nail infection can potentially affect any part of the nail, including the nail bed, nail plate or root of the nail, or in some cases may spread to the entire nail. As the infection progresses, the nail becomes discoloured, and there may be thickening of the nail bed and adjacent tissues (NICE, 2018e).

Approximately 80% of cases affect the nails of the feet, particularly the great toenails, and the condition is far more common among adults (Knott, 2015b). Onychomycosis in patients who are immunocompromised is associated with increased severity and morbidity, and may require more aggressive management (Tosti, 2020).

Diagnosis

Nail clippings can be sent to the laboratory to confirm the diagnosis if the patient is keen for treatment to be commenced. However, caution is needed as there is a high false negative rate of 40–70% (Ameen et al, 2014).

Differential diagnosis

There are a number of differential diagnoses. Onychomycosis may be mistaken for eczema, psoriasis, lichen planus, dermatitis and onychogryphosis (abnormal thickening of the nail, commonly the great toe, thought to occur as a result of previous trauma to the nail bed) (Oakley, 2003b). Other problems that may make diagnosis difficult include Darier's disease, a rare systemic disorder or yellow nail syndrome or drug reactions causing nail discoloration (Oakley, 2003b).

Complications

Secondary bacterial infections and cellulitis can occur and are more likely among those with comorbid conditions such as diabetes (Ameen et al, 2014). Patients with diabetes are at greater risk of serious complications with bacterial colonisation and vascular insufficiency exacerbating the problem and potentially leading to more serious sequelae (Tosti, 2020). One study reported that diabetic patients with onychomycosis had an approximately three times greater risk of gangrene or foot ulcer compared with diabetic patients with healthy nails (Winston and Miller, 2006).

Treatment and management

The available treatment options are as for other fungal infections and include terbinafine, itraconazole and griseofulvin. Terbinafine is generally first line, as it provides better cure rates than the alternatives (Yau et al, 2018). Topical treatment is also available and may be an option for patients who cannot tolerate oral treatment, but effect is often limited as a result of the reduced ability to penetrate the nail (Yau et al, 2018).

Prescribing tips

Terbinafine 250 mg daily may be needed for up to 3 months for nail infections and longer for toenail infections. Guidance recommends that liver function test is checked prior to starting treatment and every 4–6 weeks during treatment (NICE, 2018a). If griseofulvin is needed, the treatment will last for at least 6 months but cure rates are low and relapse rates are high (Knott, 2015b). Amorolfine will need to be applied 1–2 times a week for six months to treat fingernails and for 9–12 months to treat toenails (NICE, 2018e).

Conclusions

Fungal skin infections are a problem around the world and place a burden on healthcare resources wherever they occur. Some conditions are more easily recognisable than others and while there are similarities in treatment options available, there is a wide variation in the duration of treatment needed, with a greater risk of recurrence in some tinea infections. This article will give nurses and non-medical prescribers more confidence in recognising and treating patients who present with any of the conditions discussed.