Download An overview of athlete`s foot

AUGUST 2015 • PHARMACY PRACTICE • 13
An overview of athlete’s foot
Dr. Vivienne Mak
Senior Lecturer,
School of Pharmacy
Monash University Malaysia
Bandar Sunway, Subang Jaya
Esther Chan
Research Assistant,
School of Pharmacy
Monash University Malaysia
Bandar Sunway, Subang Jaya
Introduction
Pathogenesis
thlete’s foot (tinea pedis)
is a type of dermatophyte
(fungal) infection which occurs commonly on the interdigital
spaces, soles and sides of the
feet.1,2
It is known as athlete’s foot as
it is very common among athletes,
and the fungi that causes it is
found in areas where athletes often gather, such as locker rooms
and public showers. This infection is contagious and recurrent
in nature. The infection may also
spread causing discolouration
and thickening of the nails if the
underlying cause is not treated.1
The most common pathogens
involved in causing tinea pedis
are Trichophyton rubrum sensu
stricto, Trichophyton interdigitale
and Epidermophyton floccosum,
with T. rubrum as the most common pathogen.1–3 Athlete’s foot
is a common condition and pharmacists are often consulted to
provide advice on prevention and
management of the condition.
Tinea pedis is an infection caused
by arthrospores or asexually reproducing conidia. These organisms favour high temperatures,
alkaline pH and moist areas. Certain host factors such as damaged
skin, maceration of the skin and
immunodeficiency can facilitate
the invasion of dermatophytes.
The most common dermatophyte
infections are due to the absence
of a host factor, sebum, which
is a natural inhibitory secretion.
This fatty acid is not present in
the plantar regions and therefore,
infection may spread and occur
on the plantar areas with no sebaceous glands.1,2
The dermatophyte fungi invade the superficial keratin of the
skin by using enzymes such as
keratinases,
metalloproteases,
lipases and ceramides. Very often, the infection is confined to
the superficial layer. The immune
system responds to the invasion
of dermatophytes and a series or
immune and inflammatory reac-
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tions occur. However, certain dermatophytes such as T. rubrum,
consists of mannans on their cells
walls which can reduce the proliferation of lymphocytes, thereby
inhibiting the body’s immune response. The clinical presentation
of tinea pedis is thus dependent
on the host’s defence mechanisms and the infecting dermatophyte.1,2
Clinical presentation
Tinea pedis normally presents in
four different forms: (i) interdigital,
(ii) inflammatory (vesicular), (iii)
chronic hyperkeratotic (moccasin) and (iv) ulcerative.1
Interdigital tinea pedis
This is the most characteristic type
of tinea pedis. The most common
causative dermatophyte is T. rubrum followed by T. interdigitale.1,2
It presents with erythema, scaling,
maceration and fissuring seen
most often in the cleft between
the fourth and fifth toes. The infection often starts with scaling first,
and when the bacteria proliferate,
maceration occurs.4 Typically, the
dorsal surface of the foot is unaffected, but the neighbouring plantar areas may be involved.1,2
Inflammatory (vesicular) tinea pedis
Inflammatory or vesicular tinea
pedis is commonly caused by T.
interdigitale. These hard, tense
vesicles and lesions most often
occur on the instep of the foot.
The vesicular lesions settle deep
in the epidermis and a bullae
forms when the vesicles coalesce
together. These bullae lesions
with either clear or purulent fluid
may rupture leaving an erythematous and scaly foot. The purulent
fluid is a result of bacterial superinfection by Staphylococcus aureus or group A Streptococcus.
These lesions develop rapidly
and usually occur during warm
weather.1,2
Chronic hyperkeratotic or moccasin tinea pedis
This is another form of presentation which is most commonly
caused by T. rubrum. This type is
characterized by chronic plantar
erythema with slight scaling on
the sole of the foot and is often
associated with nail involvement.4
Diffuse hyperkeratosis may also
develop. The dry hyperkeratotic
scaling normally involves the entire plantar surface without affecting the dorsal surface of the foot.
However, lesions may spread
across the dorsal surface of the
foot in immunosuppressed patients and patients that apply topical corticosteroids.1 Patients with
this type of tinea pedis normally
will have a defect in their cell mediated immune response and are
therefore unable to mount a delayed type hypersensitivity reaction to certain dermatophytes.4
This defect may predispose some
people to tinea pedis.
Ulcerative tinea pedis
Ulcerative tinea pedis is typically
caused by T. interdigitale, similar
to inflammatory tinea pedis. It is
characterized by rapidly spreading
vesiculopustular
lesions
(macerated with scaly borders)
appearing in the web spaces and
it is frequently accompanied by a
secondary bacterial infection.1,2
In certain cases, it can be severe
enough to immobilize the patient.
This infection usually begins between the third, fourth and fifth
toes. It then extends to the lateral
CONTINUED ON PAGE 14
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FROM “AN OVERVIEW OF
ATHLETE’S FOOT” PAGE 13
dorsum and the plantar surface of
the foot. This type of tinea pedis
is normally seen in immunosuppressed or diabetic patients. The
most common complications that
may arise with this type are cellulitis, lymphangitis, fever and malaise.1,2
Prevalence
It has been reported that more
than 70 percent of the population
will have this condition at some
point in their life and approximately 15 percent of the world’s
population has tinea pedis.2,5 It
is estimated that the prevalence
in Malaysia would be relatively
high due to the hot and humid
conditions which dermatophytes
favour.6 Table 1 summarizes the
prevalence studies conducted
worldwide.
There are also studies on tinea
pedis in specific occupations and
populations. One such study was
conducted by Auger et al where
rates of tinea pedis in marathon
runners
were
explored—the
prevalence rate was 22 percent.7
Due to the chronic nature of dermatophyte infections (tinea pedis
in this case), the annual cost for
treatment is estimated to be more
than US$400 million in the US.1
Risk factors
There are many risk factors for
contracting tinea pedis. Although
it affects all ages, it is more common in adults aged 31 to 60 with
the incidence increasing with
age. Children are also less likely
to contract tinea pedis. Besides
that, men are also more likely than
women to be infected.2,3 Hot, humid, tropical environment, sweating, prolonged use of occlusive
footwear, trauma to the feet and
going to communal areas such
as swimming pools and gymnasiums where bathrooms are shared
are also risk factors for this infection.1,3,7 Moreover, certain occupational groups such as coal
miners, soldiers and marathon
runners are at a higher risk of contracting this infection as a result of
prolonged use of occlusive footwear. Furthermore, having some
form of immunodeficiency or cold
feet resulting from poor circulation may also increase the risk of
tinea pedis. Lastly, if the skin produces less fatty acid, the possibility of getting this infection is also
higher.8
Symptoms
Not everyone may experience
symptoms due to tinea pedis.
However, some may experience
bothersome symptoms. Although
these symptoms are minor, the
infection can be persistent. Some
of the symptoms include severe
itching of the foot, blistering that
itches, cracking and peeling of
the skin between the toes and
the soles, dry skin on the soles
or sides of the feet, redness and
scaling of the soles, unpleasant
odour, burning and painful sensation in some instances (inflammatory tinea pedis), and occasionally discoloured, thick and crumbly
toenails.8
Diagnosis
Tinea pedis is normally diagnosed based on symptoms and
a detailed patient history.9 However, this condition can be misdiagnosed as other scaly and
pustular skin conditions such as
psoriasis, herpetic infections, cellulitis, contact dermatitis, eczema,
erythrasma, impetigo, bacterial
toe-web infections, candidiasis
and pemphigus.1,2 Hence, to obtain a definitive diagnosis, laboratory tests may be required. These
tests include direct microscopic
examination with potassium hydroxide (KOH) preparations and
fungal culture of skin scrapings.1,9
Potassium hydroxide preparation
This test can be used to identify
fungal elements.1,2 Scaly specimen is required from the site of
infection. For lesions without fluid,
scales can be obtained from the
border or the edge of the lesion
whereas for blistering lesions,
specimen can be obtained from
the roof of the vesicle. As for pustular lesions, the purulent debris
can be used.9 A positive KOH will
show numerous septate hyphae.1
Fungal culture
A fungal culture may be performed
to confirm the diagnosis of tinea
pedis and to ascertain its pathogenic species.1,2 Sabouraud’s
glucose agar is the usual fungal
culture medium. Antibiotics may
be added to the medium to prevent bacteria from inhibiting the
growth of the pathogenic dermatophyte. Adding cycloheximide in
the media is useful to ascertain
the pathogenic species.9
Studies for differential diagnosis
To confirm the diagnosis of tinea
pedis, studies for differential diagnosis may include a bacterial
culture to rule out secondary infection; wood’s light inspection to
rule out erythasma; and skin biopsy to differentiate a dermatophyte
infection from other dermatoses.9
Complications
There are several complications of
tinea pedis which includes id reactions, bacterial superinfection,
Majocchi’s granulomas, tinea incognito, lymphangitis and cellulitis. Spreading of infection to the
nails, other skin areas and scalp
is also another complication.1
Cellulitis
Tinea pedis, especially interdigital
tinea pedis, is the most common
entry point for bacteria in cellulitis.
Dermatophytes do not cause cellulitis per se but they cause scaling and fissuring of the skin which
results in skin exposure. This provides the bacteria an open access
into the body. Patients with lower
limb cellulitis should always be
examined for tinea pedis. If results
are positive, antifungal therapy
should be administered to prevent reoccurrence.1
Id reaction
Id (dermatophytide) reaction can
be defined as an allergic rash
caused by local inflammatory
fungal infection at a distant site.
The most common cause for id
reaction is a superficial fungal
infection, specifically tinea pedis.
It has been reported that the incidence of dermatophytids due
to tinea pedis is 17 percent. The
rash is often located on the hands
Country
Subject characteristics
Prevalence
Australia6
2,491 students aged 4 to 18
Overall prevalence was 5.2 percent, increasing
in age from 2.1 percent in 4- to 6-year-olds to 9.7
percent in 16- to 18-year-olds. A higher proportion of males (6.0 percent) had tinea pedis than
females (4.3 percent).
Spain3
1,000 healthy volunteers aged 20 to
over 90.
Overall prevalence was 2.9 percent with a prevalence of 4.2 percent for men and a prevalence of
1.7 percent for women.
Libya6
1,180 patients out of the 2,224
patients attending the Dermatology
Clinics of the Tripoli Medical Centre
(TMC) were confirmed to have
fungal skin infections.
Overall prevalence of tinea pedis was 8.1 percent.
12,903 cases of superficial fungal
infections were seen at the National
Skin Centre.
Tinea pedis comprised of 27.3 percent of the
cases.
Singapore
6
Table 1: The global prevalence of tinea pedis.
and sides of the fingers.1 Treatment usually involves an antifungal agent to treat the underlying
cause and a steroid to treat the
immunological reaction.
dida species and bacteria.11
Tolnaftate is less effective than
azoles and terbinafine and it
may irritate the skin.10
4. Topical pyridones
Majocchi’s granuloma
Majocchi’s granuloma is a deep
folliculitis due to dermatophyte
invasion. This complication commonly occurs as a result of long
term usage of potent topical corticosteroids,
chemotherapeutic
agents or systemic immunosuppression on unsuspected tinea.1
Systemic antifungal agents are
usually necessary to treat this.
Pharmacological management
Medical treatment is the mainstay
of treating tinea pedis. It can be
treated with either a topical or an
oral antifungal agent or a combination of both. For topical agents,
the duration of therapy is typically
1 to 6 weeks depending on the
potency of the antifungal agent.
Early diagnosis and treatment is
recommended as this can diminish the incidence of tinea unguium (tinea of the nail).1
Topical therapy
There are several topical antifungal agents that can be used to
treat tinea pedis. The two main
classes of antifungal products are
imidazoles (clotrimazole, econazole, ketoconazole, miconazole,
oxiconazole and sulconazole)
and allylamines (naftifine and terbinafine).9
1. Topical imidazoles
Azoles such as bifonazole and
clotrimazole are the treatment
of choice.10 They are effective
in all forms of tinea pedis but
are exceptionally effective for
interdigital tinea pedis as they
are effective against dermatophytes and also Candida species. Some agents in this class
(eg, econazole) also have antibacterial activity.2
2. Topical allylamines
Allylamines are useful in treating all forms of tinea pedis.
In vitro studies have demonstrated the potent activity of
allyamines against dermatophyte fungi. Therefore, these
agents are effective in treating
patients with intractable tinea
pedis (eg, chronic hyperkeratotic tinea pedis). Patients
with this type of tinea pedis
require a longer duration of
therapy, typically 4 weeks. A
quicker response is seen for
patients with interdigital tinea
pedis (1 week).2 Although terbinafine has a faster response
rate compared to azoles (7
days for terbinafine and 2 to 4
weeks for azoles), it is expensive and less affordable for patients.10
3.Tolnaftate
Tolnaftate is a thiocarbamate
antifungal agent which may
be fungistatic or fungicidal
against susceptible fungi. It is
active against dermatophytes
but it is inactive against Can-
Pyridones (ciclopirox olamine)
are broad-spectrum agents
which target dermatophytes,
bacteria and Candida species.9 This class of drugs can
be used for all forms of tinea
pedis but it is exceptionally effective in interdigital tinea pedis, similar to the azoles.2
5. Dermatological agents
Examples of dermatological
agents include aluminum acetate (Burow’s solution), urea
and ammonium lactate lotion.
Burow’s solution is useful for
vesicular type tinea pedis as
it helps dry the lesions. Urea
and ammonium lactate lotion
are useful to decrease the
scaling in patients with hyperkeratotic soles.1,2
6.Combination with topical
corticosteroid antifungal
mixtures
Topical corticosteroids should
be used with caution as it can
exacerbate tinea infections
and result in treatment failure.
It may be used for a few days
along with topical antifungal
agents if there is inflammation of the lesions. The steroid
should only be applied onto
the lesion.1,9
7. Other agents
i. Tea tree oil
Clinical studies have suggested that tea tree oil is
effective in treating tinea
pedis. It is known to have
antimicrobial
properties
and it has been used as a
natural remedy for various
skin conditions. A study
conducted in Australia displayed marked clinical response of 25 percent and
50 percent tea tree oil with
a response rate of 72 percent for 25 percent tea tree
oil and 68 percent for 50
percent tea tree oil.12
ii.Ajoene
Ajoene is a garlic-derived
organic trisulfur which
contains antifungal activity. It has been shown
that 0.4 percent of ajoene
used topically in shortterm treatment resulted in
79 percent cure rates. This
agent may be as effective
as topical terbinafine in
treating tinea pedis and
may be a cheaper alternative to topical terbinafine.13
iii. Undecylenic acid
Undecylenic acid liquid
is a fungistatic antifungal
agent. It is less effective
compared to azoles, terbinafine and tolnaftate and it
may irritate the skin.10
iv. Whitfield’s ointment
Whitfield’s ointment consists of benzoic acid and
salicylic acid in a white soft
paraffin base. It is a cheap-
CONTINUED ON PAGE 15
AUGUST 2015 • PHARMACY PRACTICE • 15
FROM “AN OVERVIEW OF
ATHLETE’S FOOT” PAGE 14
er alternative to the other
usual antifungal preparations. However, duration
of therapy is usually longer
(up to 1 month).14
v.Oleozon
Oleozon is obtained from
the reaction of sunflower
oil and the ozone (also
known as ozonized sunflower oil). This product
has antimicrobial effects
and germicidal
action
against viruses, bacteria
and fungi. A complete clinical cure was seen in 75 out
of 100 patients (75 percent
cure rate).15 However, the
safety of this ozonized
product is still a concern in
Malaysia and more studies
are needed to confirm its
safety and efficacy.
Systemic therapy
Tinea pedis is normally responsive to topical agents. However,
oral therapy may be necessary if
there is involvement of the nails, if
infection becomes widespread or
severe, is unresponsive to topical
therapy, or is recurrent.8 Systemic
treatment is also used in patients
with extensive chronic hyperkeratotic and inflammatory/vesicular
tinea pedis. Usually, patients with
diabetes or peripheral vascular
disease and patients with immunosuppressed conditions will also
require oral treatment.2 Examples
of oral treatment are terbinafine
250 mg, griseofulvin, fluconazole
150 mg and itraconazole 200 mg.
Treatment should continue until
clinical resolution of the infection
is achieved, normally between
2 and 6 weeks. In most cases,
a 4-week course is usually sufficient. Griseofulvin requires a longer duration of therapy and has a
narrow spectrum of activity but it
is as effective and a cheaper alternative.10
To assess the effectiveness
among oral antifungal agents,
several studies have been conducted. There have been four
studies comparing terbinafine
(250 mg/day for 2 weeks) and
itraconazole (100 mg/day for 2
to 4 weeks). Three of the four tri-
als demonstrated a higher cure
rate for terbinafine.5 Besides
that, there are also studies comparing agents in the same class
(eg, azoles). The trials showed a
similar cure rate comparing ketoconazole (200 mg/day) and
fluconazole (50 mg/day) in one
trial and itraconazole (100 mg/
day) and fluconazole (50 mg/day)
in another. For studies involving
terbinafine and griseofulvin, terbinafine appeared to have better
cure rates. In summary, these trials all suggest that terbinafine is
superior compared to all the other
oral antifungal agents with a high
cure rate.5
Counselling points
Before application of the topical
antifungal agent, the affected area
should be washed and completely
dried. A thin layer of drug should
then be applied to the affected areas.10 Patients with hyperkeratotic
tinea pedis should apply the antifungal medication to the bottom
and sides of the feet. For patients
with interdigital tinea pedis, it is important to apply the medication to
the spaces between the toes and
also to the soles of the feet to prevent plantar-surface infection.1,2
Counselling on patient adherence and compliance is also important to ensure that the infection
is completely eradicated. Due to
the chronic and recurrent nature
of the infection, patients should be
advised to continue topical treatment for 2 weeks after they feel
better or after clinical signs have
resolved (terbinafine is an exception). Even after topical and systemic therapy, recurrence occurs
in up to 70 percent of patients.
Recurrence is partly caused by
reinfection of the dermatophyte
and the failure to eradicate the
original infection. The main factor
contributing to re-infection is the
persistence of infective fungal elements on the skin.9
Prevention strategies
Occlusive footwear gives rise to
infection by creating an environment where dermatophytes thrive
in. Thus, patients should try to
keep their feet dry and cool and
reduce moisture in shoes to prevent infection and also to prevent recurrence of infection. Old
or worn out shoes that may be
contributing to infection or the
recurrence of infection should be
discarded. Besides that, permeable, breathable or open-toe footwear is recommended for those
with excessive sweating. Frequent sock changes are also important particularly during warm
weather.
Moreover, it is also important
to remind patients to dry the spaces between the toes after bathing
and to use a separate towel for
infected areas. Sharing of towels
and worn garments should also
be avoided to prevent the spread
of infection. Drying agents such
as antifungal powders (miconazole), gentian violet, Burow’s
solution soaks and aluminium
chloride solution are also recom-
mended to prevent the growth of
fungi when occlusive footwear is
worn.1,8,10
Dermatophytes can survive
in chlorinated swimming pools
at temperatures of 28 to 31oC for
at least 123 days.1 Therefore, it
is important to have regular feet
washes and have protective footwear on (eg, thongs) in communal areas as contact with infected
scales or dermatophytes on bath
or pool floors may increase the
chances of infection. Frequent
washing of apparel is also recommended as infected scales can be
present on clothing as well.1,8,10
Conclusion
Tinea pedis is a common disease
of the skin and it constitutes an
important health problem to the
society albeit not life threatening.1
There are many factors which may
have contributed to the increasing incidence of tinea pedis. This
includes the aging population,
more fitness fanatical individuals
and increasing participation in
leisure-related activities such as
swimming.5 This infection has become a worldwide epidemiological and economic problem not
only to the health authorities but
also to the public.
As the saying goes ‘prevention is better than cure.’ As healthcare professionals, it is our duty to
educate the public on prevention
strategies and to have the public’s
best interest in mind, to ensure
patient compliance and comfort,
whenever recommending a drug
to them.
References: 1.Ilkit M, Durdu M. Tinea pedis: The etiology and global epidemiology of a common fungal infection. Crit Rev Microbiol 2014. doi:10.3109/1040841X.2013.856853
2. Robbins CM. Tinea Pedis. New York © 1994-2015 by WebMD LLC; [updated 2014 Dec 10 cited 2015 April 8 ]. Available at: http://emedicine.medscape.com/article/1091684overview#a0104 3. Perea S, Ramos MJ, Garau M, et al. Prevalence and risk factors of tinea unguium and tinea pedis in the general population in Spain. J Clin Microbiol 2000;38(9):3226–
3230. 4. Leyden JL. Tinea pedis pathophysiology and treatment. J Am Acad Dermatol. 1994;31(3 Pt 2):S31–33. 5. Bell-Syer SE, Khan SM, Torgerson DJ. Oral treatments for fungal
infections of the skin of the foot. Cochrane Database Syst Rev 2012;10:CD003584. 6. Havlickova B, Czaika VA, Friedrich M. Epidemiological trends in skin mycoses worldwide. Mycoses
2008;51 Suppl 4:2–15. 7. Auger P, Marquis G, Joly J, et al. Epidemiology of tinea pedis in marathon runners: prevalence of occult athlete’s foot. Mycoses 1993;36(1–2):35–41. 8. DermNet NZ. Tinea Pedis © 2015 DermNet New Zealand Trust; [updated 2014 Sep 23 cited 2015 Apr 9]. Available at: http://dermnetnz.org/fungal/tinea-pedis.html 9. Drake LA, Dinehart
SM, Farmer ER, et al. Guidelines of care for superficial mycotic infections of the skin: tinea corporis, tinea cruris, tinea faciei, tinea manuum, and tinea pedis. Guidelines/Outcomes Committee. American Academy of Dermatology. J Am Acad Dermatol 1996;34(2 Pt 1):282–286. 10. Tinea. In: Australian Medicines Handbook 2015 [Internet]. Adelaide Australian Medicines
Handbook Pty Ltd. Available at: https://amhonline.amh.net.au.ezproxy.lib.monash.edu.au/chapters/chap-08/fungal-yeast-infections/tinea.t 11. Drugs.com. Tolnaftate Bethesda
© 2000-2015 Drugs.com; 2004 [cited 2015 Apr 15]. Available at: www.drugs.com/monograph/tolnaftate.html 12. Satchell AC, Saurajen A, Bell C, et al. Treatment of interdigital tinea
pedis with 25% and 50% tea tree oil solution: a randomized, placebo-controlled, blinded study. Australas J Dermatol 2002;43(3):175–178. 13. Ledezma E, Marcano K, Jorquera A, et al.
Efficacy of ajoene in the treatment of tinea pedis: a double-blind and comparative study with terbinafine. J Am Acad Dermatol 2000;43(5 Pt 1):829–832. 14. IFD. Management of Tinea
Pedis United Kingdom: ©IFD 2015; [cited 2015 Apr 16 ]. Available at: www.ifd.org/protocols/tinea-pedis 15. Menéndez S, Falcón L, Simón DR, et al. Efficacy of ozonized sunflower
oil in the treatment of tinea pedis. Mycoses 2002;45(8):329–332.
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